Networking Problems WinXP to WinXP Home.

I am having problems with my networking. I have 3 PCs, all WinXP Pro. One laptop WinXP Home.
The Laptop can access all pcs. I can view/modify all shared folders/drives on all PCs.. BUT, None of the PCs can access the laptop. It shows in the WorkGroup Computers. But is says “Permission Denied” or Access denied. I have no option to set permissions anywhere. I have looked for them.
Any advice would be greatly appreciated. email privately, or here. Thanks in Advance