|Your USB flash drive may not work properly in all USB ports you try it in.|
See response 3 in this:
If that doesn't help...
You are supposed to click on the grey rectangular icon with the green arrow on it in your taskbar whenever you unplug a USB flash drive while the computer is still running and you are in Windows, and click on Safely remove USB Mass Storage Device (it may be hidden and you have to click on the < at the left of the icons in the taskbar to show it) - have you been doing that?
If you haven't you may have damaged the data on the flash drive.
If that's your case, it won't work properly in any USB port on any computer. (If it does work fine on other computers you have a different problem.)
You can usually use the drive normally again no problem but you will probably have to delete the partition on it and make a new one and all the data that was on it probably cannot be recovered.
You can't delete the partition on it in XP itself by default. You have to do it some other way.
hp flash drive formatter
Click on Primary Download Site
"This utility will format any USB flash drive, with your choice of FAT, FAT32, or NTFS partition types."
Usually you use FAT partitioning for a partition of 2gb or less, and FAT32 for a partition of more than 2gb - it is not recommended for you to use NTFS partitioning for any partition on a flash drive or a hard drive that is 4gb or less.