Cannot share USB hard drive

I have two computers on my wired home network, one running WinXP SP2 and the other an elderly laptop with Win98. Generally, the network works well and everything talks to each other, incuding access to shared folders on the XP machine's fixed HD. On the WinXP computer I have a USB connected external HDD, but when I try to share folders on that, the Laptop gives "access denied....not enough memory..". When I go into the XP machine and try to select the same shared folder, I get a similar message with something like "insufficient memory for server". The external drive is NTFS formatted (as is the XP machine's HDD) and is mounted as an NTFS folder. The only difference seems to be that it's a USB connected drive. I can share any folder on the fixed HDD.

Has anyone any suggestions?

 

I think I've found the answer - IRPStackSize too small in HKEY_LOCAL_MACHINE\System\CourrentControlSet\Services\LanmanServer\Parameters.

However when I went into Registry Editor I found I've got TWO CurrentControlSets - 0001 and 0002. As far as I can tell, the contents are the same. Do I change one or both?