usb 2.0 external hard drive is not assigned with a drive letter

>I appreciate it if someone could help me on this
> frustrating problem:
> i recently bought a 60 GB usb 2.0 hard disk drive. My
> computer seemed regconizing it: sounds played when
> plugging in and out, 'safely remove hardware' icon showed
> up on the right bottom corner, double clicks on the icon
> showed: mass storage device in its list, double click on
> this line showed: usb 2.0 hard disk drive; from control
> panel/system/hardware/device manager/hard drives/usb 2.0
> storage device/volume showed no info but when clicked
> on 'populate' showed 'new volume' with 57GB.
> The problem is in the 'my computer' there was no drive
> letter that allowed its use. Plugging it in my other
> computer and laptop (also MS XP), the drive letter showed
> under 'new volume' and was able to use.
> One thing worth mentioning, the trouble computer seems
> has problem with 2 USB ports. In the 'other device'
> item, 2 'USB device' icons showed with a yellow question
> marks. When rebooted, it attempt to install the drivers
> but failed to do so. However, there are two other usb 2.0
> ports without problem. Plugging the usb hard drive there
> had the same problem.
> Please help. How can I make the drive letter show up for
> use.
> Thanks a lot,
> Thao