I dont think i understand how you have the two pc's connected?
"I have two computers at home, both with a network adapter and a cable connecting them (i think the description of the cable is a crossbred cable, but i'm not really sure, that's not the problem). On one computer I have WinXP Home Edition, and on the other XP Proffesional SP1"
Does this mean that you have a Network Card on pc1 and a network card on pc2, then a crossover cat5e cable running from pc1 into pc2. If so, this is not the normal means of connecting two pc's together, normally one passes through a router, switch, or hub. But do not despair... I have done this in my Dial up days (before I could afford broadband - for gaming).
You have said that so far you are able to show a connection between the computers and ping one to the other, and that internet sharing and Lan games work. On the Part of Internet sharing I dont know how you accomplished that unless the first pc has 2 network cards in it. Can you clarify that part for me?....
YOUR ACTUAL PROBLEM...
BUT, I CAN'T get the two computers to share "normal" windows resources - printers, scanners, folders! In fact, when I check each of them for "Neighborhood friends", each computer only sees itself in the group. now I think I set both to the same group name, as I see in System Properties tab (right-click my computer, properties,...)
Solution 1 - to be done on both PC's
first open 'My Computer' and browse to the drive or directory you wish to share. Right click the drive or directory and select 'sharing and security.' Under 'network sharing and security' select the 'enable sharing of files without running the network wizard' option. Select 'share this folder/drive on the network'
Share name specifies the name that will appear for the share on remote computers. Check the 'allow network users to change my files' box if you want remote users to be able to add, delete or modify files within the folder or drive. By default it is unchecked, giving read-only access. Click ok.
Solution 2 - to be done on both PC's
If your are still unable to share then try to run your network setup wizard on both machines again(make sure to give both Pc's the EXACT same workgropup name...(mkae sure to reboot both pc's afterwards) If you need assistance with this let me know.
Solution 3 - to be done on both PC's
If this does not resolve your problem then you must verify that both PC's have the latest security updates and patches available from windows updates. Once you have done that, again run the network setup wizard and reboot both pc's.
Solution 4 - to be done on both PC's
If these steps do not work, check and see what firewalls, security programs, and active virus scanners you have running in the background. Temporarily disable all of these then try to view the workgrpoup computers again.
After you have tried all of the steps listed above and if you are still not able to share files, then post back and we will investigate further.