File Sharing--Access Denied

[SturmWork]

I've had this problem for quite some time now and it's finally gotten to the point that it's frustrated me enough to post it here.
I have two computers at work here. They are both running Windows XP Pro and are connected via 100BaseT ethernet to a LinkSys router with DHCP enabled. The two PCs have no trouble at all seeing each other and accessing the internet. I want to be able to share files between both computers, which have Simple File Sharing enabled (let's call them A and B). Unfortunately, the File Sharing is only working in one direction. PC A can read and write files on PC B, but not the other way 'round. PC B gives me an error message the instant I click on a shared folder on PC A: "C:\WHATEVER is not accessible. You might not have permission to access this network resource. Blah blah blah. Access is denied."
I do not really want to have to create new user accounts just to share a few files, so I'd rather use the built-in Guest accounts, of course. I've heard a rumor that in order to do so, I may need to tweak something in Computer Management/Services. Any ideas on what I can do? Thanks.

[leeg]

Did you try giving full control of the drive to the guest, Right click the drive you want to share> select Properties> Sharing and security Tab and click on the permissions button> click the Add button> and type "guest" then press ok> set the permissions of guest to full control(for now just for test) then see if you can access the drive maybe by mapping the drive to the other computer

[SturmWork]

Actually, I have Simple File Sharing enabled on both PCs, so I don't have a "Permissions" button. Just a checkbox for allowing/denying write access to the shared drive/folder. Strange thing, though. I went back into my C: drive's Sharing properties, unchecked the "Shared" box, then rechecked it, and hit "Apply." It took quite a few minutes as it re-scanned the entire drive and, presumably, set access levels for all files & folders. When it was done, everything worked smoothly. Wish I knew why it didn't work the day before and all those months earlier!

[leeg]

Excellent job!