Hi. I was facing this same problem just 3 mins back. I have 2 computers, both Win XP SP2, with USB 2.0 ports and connected to the internet. I transfered data to my 250GB external HDD but couldnt read a few files on the other system. Problem was not with all files... just a few. Each system that had uploaded the data onto the drive could access but the other system couldnt.
Then I came across the following documents.
http://www.techspot.com/vb/all/windows/t...00-install.html
http://support.microsoft.com/default.aspx?scid=kb;en-us;308421&Product=winxp
Enjoy.