This seems to be quite a common problem with XP. Try this fix :
Start Registry Editor - Go to Start-->Run, type regedit
Locate the UpperFilters & LowerFilters value under the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}
Back up the entry first by highlighting the {4D36E965-E325-11CE-BFC1-08002BE10318}. Then go up to, File and select Export, enter any name you want and save it where you can find it.
Now delete 2 entrys within {4D36E965-E325-11CE-BFC1-08002BE10318}
Highlight {4D36E965-E325-11CE-BFC1-08002BE10318} and look on the right for the entry, "UpperFilters", right click on it and select delete. Now do the same for LowerFilters
Now reboot & scan for new hardware if XP doesn't automatically detect the drives.
If this doesn't work or goes wrong, you can just import the saved key back into the registry.