Windows XP keeps a record of all files on the hard disk so when you do a search on the hard drive it is faster because of the indexed files. There is a downside to this and because the computer has to index all files, it will slow down normal file commands like open, close, etc.
If you do not do a whole lot of searches on your hard drive then you may want to turn this feature off:
Open My Computer.
Right-click your hard drive icon and select Properties.
At the bottom of the window you’ll see "Allow indexing service to index this disk for faster searches," uncheck this and click ok.
A new window will pop up and select Apply to all folders and subfolders.
It will take a minute or two for the changes to take affect but then you should enjoy slightly faster performance.