大家知道，Windows系統文件按照不同的格式和用途分很多種類，為便於管理和識別，在對文件命名時，是以擴展名加以區分的，即文件名格式為: "主文件名.擴展名"。這樣就可以根據文件的擴展名，判定文件的種類，從而知道其格式和用途。例如：
"文件名1.DOC"的擴展名"DOC"表示本文件是壹個"Microsoft Word 文檔"，
"文件名2.XLS"的擴展名"XLS"表示本文件是壹個"Microsoft Excel 工作表"，
"文件名3.BMP"的擴展名"BMP"表示本文件是壹個"BMP格式圖像"，
"文件名4.MP3"的擴展名"MP3"表示本文件是壹個"MP3 格式聲音"，
"文件名5.MPEG"的擴展名"MPEG"表示本文件是壹個"電影文件(MPEG)"。
下面列出Windows系統文件的擴展名及其分類對照表，以備查閱：
1. "323" "H.323 Internet 電話技術"
2. "386" "虛擬設備驅動程序"
3. "ACA" "Microsoft Agent Character File (HTTP format)"
4. "ACF" "Microsoft Agent Character File (HTTP format)"
5. "ACG" "Microsoft Agent 預覽文件"
6. "ACL" "自動更正列表文件"
7. "ACS" "Microsoft Agent Character File"
8. "ACW" "輔助功能向導設置"
9. "ADE" "Microsoft Access 項目擴展"
10. "ADN" "Microsoft Access 空白項目模板"
11. "ADP" "Microsoft Access 項目"
12. "AIF" "AIFF 格式聲音"
13. "AIFC" "AIFF 格式聲音"
14. "AIFF" "AIFF 格式聲音"
15. "ANI" "動畫光標"
16. "ASA" "活動服務器文檔"
17. "ASD" "ASF Stream Description File"
18. "ASF" "Windows Media 音頻/視頻文件"
19. "ASP" "活動服務器文檔"
20. "ASX" "Windows Media 音頻/視頻快捷方式"
21. "AU" "AU 格式聲音"
22. "AUDIOCD" "AudioCD"
23. "AVI" "視頻剪輯"
24. "AW" "應答向導文件"
25. "BKF" "Windows 備份文件"
26. "BLG" "性能監視器文件"
27. "BMP" "BMP 圖像"
28. "CAT" "安全編錄"
29. "CDA" "CD 音頻曲目"
30. "CDF" "頻道文件"
31. "CDX" "活動服務器文檔"
32. "CER" "安全證書"
33. "CHK" "還原了文件碎片"
34. "CHM" "已編譯的 HTML 幫助文件"
35. "CLP" "剪貼板剪貼"
36. "CNF" "快速撥號"
37. "COL" "HTML 幫助文件"
38. "CPL" "控制面板擴展"
39. "CRL" "證書吊銷列表"
40. "CRT" "安全證書"
41. "CSS" "級聯樣式表文檔"
42. "CSV" "Microsoft Excel 逗號分隔值文件"
43. "CUR" "光標"
44. "DB" "數據庫文件"
45. "DCS" "數據庫內容源"
46. "DER" "安全證書"
47. "DESKLINK" "DESKLINK 文件"
48. "DET" "Office Data File"
49. "DIB" "BMP 圖像"
50. "DIC" "文本文檔"
51. "DIF" "Microsoft Excel 數據交換格式"
52. "DOC" "Microsoft Word 文檔"
53. "DOCHTML" "Microsoft Word HTML 文檔"
54. "DOCMHTML" "DOCMHTML 文件"
55. "DOT" "Microsoft Word 模板"
56. "DOTHTML" "Microsoft Word HTML 模板"
57. "DQY" "Microsoft Excel ODBC 查詢文件"
58. "DRV" "設備驅動程序"
59. "DSN" "數據源名稱"
60. "DUN" "撥號網絡文件"
61. "DVD" "DVD"
62. "ECS" "Exchange Server 內容源"
63. "ELM" "Microsoft Office 主題文件"
64. "EMF" "EMF 圖像"
65. "EML" "Outlook Express 郵件消息"
66. "EXC" "文本文檔"
67. "FAD" "Office 數據文件"
68. "FAV" "FAV 文件"
69. "FCS" "文件***享內容源"
70. "FFA" "文件檢索索引"
71. "FFL" "文件檢索索引"
72. "FFT" "文件檢索索引"
73. "FFX" "文件檢索索引"
74. "FON" "字體文件"
75. "FPDOCLIB" "Microsoft FrontPage Document Library"
76"FPHOMEOP" Microsoft FrontPage Home Page Open"
77. "FPHOMEPG" "Microsoft FrontPage 主頁"
78. "FPHTML""Microsoft FrontPage HTML 文檔"
79. "FPLIST" "Microsoft FrontPage List"
80. "FPNOPUB" "Microsoft FrontPage Dont Publish"
81. "FPOPEN" "Microsoft FrontPage 打開文件"
82. "FPSURVEY" "Microsoft FrontPage Survey"
83. "FPWEB" "FPWEB 文件"
84. "FRG" "FRG 文件"
85. "GIF" "GIF 圖像"
86. "GRA" "Microsoft Graph 圖表"
87. "GRP" "Microsoft 程序組"
88. "HLP" "幫助文件"
89. "HOL" "Microsoft Outlook Holidays"
90. "HT" "超級終端文件"
91. "HTA" "HTML Application"
92. "HTC" "HTC 文件"
93. "HTM" "HTML Document"
94. "HTML" "HTML Document"
95. "HTT" "HyperText 模板"
96. "HTX""用於 Internet 數據庫的 HTML 模板"
97. "ICC" "ICC 配置文件"
98. "ICM" "ICC 配置文件"
99. "ICO" "圖標"
100. "ICS" "iCalendar 文件"
101. "IDC" "IDC 文件"
102. "III" "Intel IPhone 兼容"
103. "INF" "安裝信息"
104. "INI" "配置設置"
105. "INS" "Internet 通訊設置"
106. "IQY" "Microsoft Excel Web 查詢文件"
107. "ISP" "Internet 通訊設置"
108. "ITS" "Internet Document Set"
109. "ITSS" "Microsoft Infotech Storage System File"
110. "IVF" "Indeo 視頻文件"
111. "JFIF" "JPEG 圖像"
112. "JOB" "任務對象"
113. "JOD" "Microsoft.Jet.OLEDB.4.0"
114. "JPE" "JPEG 圖像"
115. "JPEG" "JPEG 圖像"
116. "JPG" "JPEG 圖像"
117. "JS" "JScript Script File"
118. "JSE" "JScript Encoded Script File"
119. "LDB" "Microsoft Access 記錄鎖定信息"
120. "LEX" "詞典文件"
121. "LOG" "文本文檔"
122"LWV" Microsoft Linguistically Enhanced Sound File"
123. "M1V" "電影文件(MPEG)"
124. "M3U" "M3U 文件"
125. "MAD" "Microsoft Access 模塊快捷方式"
126. "MAF" "Microsoft Access 窗體快捷方式"
127. "MAG" "Microsoft Access 圖表快捷方式"
128. "MAM" "Microsoft Access 宏快捷方式"
129. "MAPIMAIL" "MAPIMAIL 文件"
130. "MAQ" "Microsoft Access 查詢快捷方式"
131. "MAR" "Microsoft Access 報表快捷方式"
132. "MAS"Microsoft Access 存儲過程快捷方式"
133. "MAT" "Microsoft Access 表快捷方式"
134. "MAU" "MAU 文件"
135. "MAV" "Microsoft Access 視圖快捷方式"
136"MAW"Microsoft Access 數據訪問頁快捷方式"
137. "MDA" "Microsoft Access 加載項"
138. "MDB" "Microsoft Access 應用程序"
139. "MDBHTML" "Microsoft Access HTML 文檔"
140. "MDE" "Microsoft Access MDE 數據庫"
141. "MDN""Microsoft Access 空白數據庫模板"
142. "MDT" "Microsoft Access 加載項數據"
143. "MDW" "Microsoft Access 工作組信息"
144. "MDZ""Microsoft Access 數據庫向導模板"
145. "MGC" "媒體目錄文件"
146. "MHT" "MHTML Document"
147. "MHTML" "MHTML Document"
148. "MID" "MIDI 序列"
149. "MIDI" "MIDI 序列"
150. "MML" "媒體目錄文件"
151. "MMM" "媒體剪輯"
152. "MMW" "媒體目錄文件"
153. "MP2" "電影文件(MPEG)"
154. "MP2V" "電影文件(MPEG)"
155. "MP3" "MP3 格式聲音"
156. "MPA" "電影文件(MPEG)"
157. "MPE" "電影文件(MPEG)"
158. "MPEG" "電影文件(MPEG)"
159. "MPF" "Media Package 文件"
160. "MPG" "電影文件(MPEG)"
161. "MPV2" "電影文件(MPEG)"
162. "MSC" "Microsoft 通用管理文檔"
163. "MSG" "Outlook 項目"
164. "MSI" "Windows Installer 軟件包"
165. "MSP" "Windows Installer 修補程序"
166. "MSRCINCIDENT" "Microsoft 遠程訪問事件"
167. "MSSTYLES" "Windows 可視化風格文件"
168. "MSWMM" "Windows Movie Maker 項目"
169. "NCS" "Lotus Notes 內容源"
170. "NFO" "MSInfo 文檔"
171. "NICK" "Office 數據文件"
172. "NK2" "Office 數據文件"
173."NMW""Microsoft NetMeeting T126 兼容白板文檔"
174. "NWS" "Outlook Express 新聞消息"
175. "OBD" "OBD 文件"
176. "OBT" "OBT 文件"
177. "OBZ" "OBZ 文件"
178. "OCX" "ActiveX 控件"
179. "ODC" "Microsoft Office 數據連接"
180. "ODCCUBEFILE" "ODCCUBEFILE 文件"
181. "ODCDATABASEFILE" "ODCDATABASEFILE 文件"
182. "ODCNEWFILE" "ODCNEWFILE 文件"
183. "ODCTABLEFILE" "ODCTABLEFILE 文件"
184. "OFT" "Outlook 項目模板"
185. "OPC" "Microsoft 清理向導文件"
186. "OPS" "Office 10 設置文件"
187. "OQY" "Microsoft Excel OLAP 查詢文件"
188. "OSS" "Office 搜索"
189. "OST" "Office 數據文件"
190. "OTF" "OpenType 字體文件"
191. "P10" "證書申請"
192. "P12" "Personal Information Exchange"
193. "P7B" "PKCS #7 證書"
194. "P7C" "數字標識文件"
195. "P7M" "PKCS #7 MIME 消息"
196. "P7R" "PKCS #7 證書"
197. "P7S" "PKCS #7 簽名"
198. "PAB" "Office 數據文件"
199. "PBK" "撥號電話簿"
200. "PCB" "PCB 文件"
201. "PCD" "Photo CD 圖像"
202. "PCX" "PCX 圖像"
203. "PFM" "Type 1 字體文件"
204. "PFX" "Personal Information Exchange"
205. "PIP" "Microsoft Office 設置文件"
206. "PKO" "公鑰安全對象"
207. "PMA" "性能監視器文件"
208. "PMC" "性能監視器文件"
209. "PML" "性能監視器文件"
210. "PMR" "性能監視器文件"
211. "PMW" "性能監視器文件"
212. "PNG" "PNG 圖像"
213. "POT" "Microsoft PowerPoint 模板"
214. "POTHTML" "Microsoft PowerPoint HTML 模板"
215. "PPA" "Microsoft PowerPoint 加載項"
216. "PPS" "Microsoft PowerPoint 幻燈片放映"
217. "PPT" "Microsoft PowerPoint 演示文稿"
218. "PPTHTML" "Microsoft PowerPoint HTML 文檔"
219. "PPTMHTML" "PPTMHTML 文件"
220. "PRF" "msrating.dll,-3001"
221. "PST" "Office 數據文件"
222. "PSW" "Password Backup"
223. "PWZ" "Microsoft PowerPoint 向導"
224. "QDS" "目錄查詢"
225. "RAT" "msrating.dll,-3000"
226. "RDP" "遠程桌面連接"
227. "REG" "註冊表項"
228. "RMI" "MIDI 序列"
229. "RNK" "撥號快捷方式"
230. "RQY" "Microsoft Excel OLE DB 查詢文件"
231. "RTF" "RTF 格式"
232. "RWZ" "Office 數據文件"
233. "SC2" "Microsoft Schedule+ 應用程序"
234. "SCD" "Microsoft Schedule+ 應用程序"
235. "SCH" "Microsoft Schedule+ 應用程序"
236. "SCP" "文本文檔"
237. "SCT" "Windows Script Component"
238. "SDB" "Appfix 軟件包"
239. "SHB" "將快捷方式插入到文檔"
240. "SHS" "片段對象"
241. "SHTM" "HTML Document"
242. "SHTML" "HTML Document"
243. "SLK" "Microsoft Excel SLK 數據導入格式"
244. "SLL" "SLL 文件"
245. "SND" "AU 格式聲音"
246. "SNP" "Snapshot 文件"
247. "SPC" "PKCS #7 證書"
248. "SPL" "Shockwave Flash Object"
249. "SST" "Microsoft 系列證書存儲"
250. "STF" "Microsoft 安裝文件"
251. "STL" "證書信任列表"
252. "STM" "HTML Document"
253. "SWF" "Shockwave Flash Object"
254. "SYS" "系統文件"
255. "TCS" "Tahoe Server 內容源"
256. "THEME" "Windows 主題文件"
257. "TIF" "TIF 圖像"
258. "TIFF" "TIF 圖像"
259. "TTC" "TrueType Collection 字體文件"
260. "TTF" "TrueType 字體文件"
261. "TXT" "文本文檔"
262. "UDL" "Microsoft 數據鏈接"
263. "ULS" "Internet 定位服務"
264. "URL" "Internet 快捷方式"
265. "VBE" "VBScript Encoded Script File"
266. "VBS" "VBScript Script File"
267. "VCF" "vCard 文件"
268. "VCS" "vCalendar 文件"
269. "VXD" "虛擬設備驅動程序"
270. "WAB" "數字標識文件"
271. "WAV" "波形聲音"
272. "WAX" "Windows Media 音頻快捷方式"
273. "WBK" "Microsoft Word 備份文檔"
274. "WCS" "Web 站點內容源"
275. "WEB" "Office 數據文件"
276. "WEBPNP" "Webpnp"
277. "WHT" "Microsoft NetMeeting 舊白板文檔"
278. "WIZ" "Microsoft Word 向導"
279. "WIZHTML" "Microsoft Access HTML 模板"
280. "WLL" "WLL 文件"
281. "WM" "Windows Media 音頻/視頻文件"
282. "WMA" "Windows Media 音頻文件"
283. "WMD" "Windows Media Player 下載軟件包"
284. "WMF" "WMF 圖像"
285. "WMP" "Windows Media Player 文件"
286. "WMS" "Windows Media Player 外觀文件"
287. "WMV" "Windows Media 音頻/視頻文件"
288. "WMX" "Windows Media 音頻/視頻快捷方式"
289. "WMZ" "Windows Media Player 外觀程序包"
290. "WPS" "WPS 文件"
291. "WRI" "寫入文檔"
292. "WSC" "Windows Script Component"
293. "WSF" "Windows Script File"
294. "WSH" "Windows Script Host Settings File"
295. "WTX" "文本文檔"
296. "WVX" "Windows Media 音頻/視頻快捷方式"
297. "XLA" "Microsoft Excel 加載宏"
298. "XLB" "Microsoft Excel 工作表"
299. "XLC" "Microsoft Excel 圖表"
300. "XLD" "Microsoft Excel 5.0 對話框編輯表"
301. "XLK" "Microsoft Excel 備份文件"
302. "XLL" "Microsoft Excel XLL 加載宏"
303. "XLM" "Microsoft Excel 4.0 宏"
304. "XLS" "Microsoft Excel 工作表"
305. "XLSHTML" "Microsoft Excel HTML 文檔"
306. "XLSMHTML" "XLSMHTML 文件"
307. "XLT" "Microsoft Excel 模板"
308. "XLTHTML" "Microsoft Excel HTML 模板"
309. "XLV" "Microsoft Excel VBA 模塊"
310. "XLW" "Microsoft Excel 工作區"
311. "XML" "XML 文檔"
312. "XNK" "Exchange 快捷方式"
313. "XSL" "XSL 樣式表"
314. "ZAP" "軟件安裝設置"
315. "ZIP" "壓縮(zipped)文件夾"