I have an odd problem with my external hard drive when I have my drive connected (via usb) ill be able to access the 2nd partition on my drive then after a few minutes the 2nd partition will be unaccessible and sometimes an error message will pop up on my screen saying that one of the partitions on the drive cannot be accessed. Iv'e reinstalled windows twice after the first reinstall my hard drive worked again but my computer crashed later and i had to unplug the drive from the usb port before I restarted windows, after the computer came back on (I ran scandisk on the internal HD from dos) I plugged in my external hard drive and both partitions worked fine for a short while then I lost access to the second partion then the first, I tryed to run scandisk on the external HD but scandisk kept telling me that a disk utility locked the drive etc. I edited the items that startup when I turn the computer on using msconfig and restarted the computer with the bare minimum of programs running, no luck. I reinstalled windows again and the drive worked again I ran scandisk on the first partion of the external usb drive and there were no errors, I'm worried that if the computer crashes again (it will ) that the external hard drive will stop working again.
Any suggestions on how to solve this mystery?

System Specs.
OS: Windows 98
cpu:1.4ghz celeron (overdrive processor)
motherboard:Intel 440BX
ram: 448MBs
external hard disk: Western Digital dual combo drive (wd1200bb)
note: I know that my computer has usb 1.1 ports and the drive can use 2.0 but this drive has been working fine for almost a year.