Word Documents cannot be copied

Hi people

I have 2 PCs, one with Win98 and one Win2000. I regularly try and copy about 120 MS Word docs from my hard drive to my usb zip drive using Windows Explorer. Half way thru the list, usually exactlly half way, Explorer bombs out and gives an error message. The same thing happens all the time on both machines with the different word docs.

Both PCs have tons of RAM and high specs.

Help!

Thanks
Bruce