The below is how Microsoft have "limited" the "Server" service (this is located in the Services part of the control panel) on all Windows home systems (that is not a “Server” OS), this service alone is the one that "serves" the shares you setup on any Windows computer newer than Windows NT4 (2000, XP, Vista, 7 and all Server OS).
This assumes you only use TCP/IP, to access the shares, and the symptoms i have noticed and how to fix them...
Windows XP service a share
When trying to access more than about 7000 files (like loading the directory into RC then it scanning them) the Windows XP OS will slow down by about 1000 times, the hard drive may look "stuck on", you can still see shares, however the desktop is super slow, the recovery here is to restart the server service in the control panel services, this will also restart the Computer service (this is fine), no system restart is needed, however you will cut of any file that was in use over the share (which by now have hung in a limbo open “not doing anything” state)
When trying to access more than about 7000 files (like loading the directory into RC then it scanning them) OR trying to copy a large file over 3Gb in size to or from a Windows 7 share the computer takes all shares offline, when you try to browse or see this computer in the network it tells you that you no longer have access, again restarting the server service will fix this.
There can be another problem i have notice in Windows 7, while you are accessing a share from a Windows 7 PC, if you receive the error "Not enough server storage is available to process this command.",, i bumped in to this pulling files from my Windows 7 64bit workstation to my MAC OSX system This is a symptom of the same problem above, however there is a Microsoft Registry fix for this (USE AT YOUR OWN RISK).http://support.microsoft.com/kb/198386
The above assumes you already have sharing working with out problems, the above is in no way explaining how to setup sharing, only to help IF you have bumped in to what seems like a damaged version of Windows when really this turns out to Microsoft OS flaws.
There are many problems in getting Windows 7 to publish it shares in a standard way so Windows XP can see them, I never use the “Home Group” method, however this forum is not the place to explain share setups.