Guys, just one short thought: what kind of drive is the H-drive? Internal? What size? What age? What type?
If it’s a relatively new drive, then it might well be a 4k-format drive. When you need to read a lot of data from that one on a Win XP system (like a virus scan does), it is crucial that it had been partitioned correctly. (E.g. Western Digital offers a special tool to do so, even afterwards the initial partiotioning) The WinXP own partitioning will not do so by default!
If you fail to align the partition correctly, performance will break down extremely.
http://www.bit-tech.net/hardware/storage/2010/04/01/the-facts-4k-advanced-format-hard-disks/2
A quote from above link (page 6):
“One thing that hit us while testing was how slow the new EARS disk was after installing Windows XP before running the WD Align utility. The installation took notably longer than usual, and the disk ground to a complete halt when tried to install the chipset drivers upon the completion of the OS install. Rebooting and running the WD Align straightaway cured the issue, and we didn’t need the software at all after that. Every time a new partition was created, the WD Align utility had to be run, but at least it only had to be run the once, and not continually as a background service.”