Slow network file transfer

I tried to transfer a file between two computers, both running
WinXP/Home-SP-1a connected with 802.11g.
I tried to drag and drop between folders.
I tried Right-click Copy to Folder.
I tried Copy and Paste from one folder to the Desktop on the other computer.

All three worked - but it took more than 30 min. to transfer a 256K file.
There was no indication that my transfer worked at the time of
drop/copy/paste. Later, while I was at lunch, all three transfer bars showed
up and completed.

What is going on?

Rick C.