It seems like there could be a couple of issues causing your USB hard drive to not be recognized by your Windows XP and Windows 7 computers:
1. File System Corruption: The drive may have experienced file system corruption, causing Windows to prompt you to format the drive. This corruption could have occurred due to unplugging the drive without safely ejecting it or other factors.
2. Drive Letter Conflict: There might be a drive letter conflict that is preventing Windows from properly recognizing the drive.
To address the issue without formatting the drive and risking data loss, you can try the following steps:
### Steps to Try:
1. Check Drive in Disk Management:
- Right-click on "My Computer" or "This PC" and...