The below program may be what you need for USB.

Desktop System Software (DSS) is a utility that provides critical updates and patches for your operating system. Install the DSS program to gain SUPPORT for Dell 3.5-inch USB floppy drives, CD-ROM/CD-RW/DVD drives, and USB devices. DSS is necessary for correct operation of your Dell computer. DSS automatically detects your computer and operating system and installs the updates appropriate for your configuration.


http://support.dell.com/support/downloads/download.aspx?c=us&l=en&s=gen&releaseid=R104418&SystemID=DIM_PNT_P4_8400&os=WW1&osl=en&deviceid=6317&devlib=0&typecnt=1&vercnt=4&formatcnt=1&libid=7&fileid=134821GX1_MAN, yes, that's the .exe file I downloaded, unzipped, and tried to install. It's for the dimension 8400 series.

I did have to reinstall Windows XP yesterday, because one of the hard drives in my RAID 1 array failed and the system crashed.

i lost many software APPLICATIONS and drivers. i'm not sure if service pack 2 is INSTALLED, although the Win XP installation CD includes SP2. I've been trying to reinstall drivers and software I lost.street1, thank you. i'll try installing that after repair install is complete. hopefully, all will be fine.You can also contact Dell support. In the USA: 888-560-8324.