First of all, you should find out if your computer is able to detect your USB Hard Disk (HDD). If it can, you should see the new HDD in Windows Explorer.
For example, if you already have 2 internal HDDs, they should occupy 2 drive letters (C: and D:). Normally, you would have one DVD drive, this DVD should use the letter E:. After you plug in your USB HDD, it should occupy the next drive letter, that is Drive F:.
If you see Drive F:, that means your computer can detect the new drive you've just plugged in. Now you can right click My Computer and select Manage. Choose [Device Manager] under [System Tools]. On the right pane, you will see [Disk Drives]. Expand Disk Drives by clicking on the "+" and you will see the all HDD information.
If you do not see the USB HDD in Win Explorer, that could mean there is something wrong with your USB device or the HDD.
下列是「裝置管理員」可能顯示裝置為「無法辨識的裝置」的最常見理由。
沒有安裝裝置驅動程式
無法取得裝置的驅動程式時,裝置管理員會顯示裝置為 [無法辨識的裝置],並且放置在 [其他裝置] 分支內。這個情形在通用序列匯流排 (USB) 以及電子電機工程師協會 (IEEE) 1394 磁碟機複合裝置十分常見。另外,檢視裝置管理員中的裝置內容時,可能會出現 [錯誤碼 1] 或 [錯誤碼 10] 的狀態。
注意:大部分的 USB 及 IEEE 1394 裝置設計為不需要額外的驅動程式就能正確地運作,因為 Windows 內含這些匯流排類型設計的驅動程式會做好這些裝置的設定。因此,如果驅動程式不適用已定義及預先提供的 Windows 類別驅動程式,就需要其他的驅動程式。如果匯流排無法辨識驅動程式,則匯流排會將這個驅動程式解譯為複合裝置,然後在裝置管理員中回報為無法辨識的裝置。
For more information, please see
http://support.microsoft.com/kb/314464/zh-tw.
2009-05-12 10:49:25 補充:
Someone said: "電腦話無法識別個硬碟,可能係你之前無用安全移除裝置,導致咁樣。"
This is absolutely wrong. 這個說法絶對錯誤。無用安全移除裝置,可致 data corruption (file 損壞) , 不會損壞 HDD。