The IRPstacksize might be too small if antivirus software is installed and fail to allow shared folders to be seen on other network computers.
Increase to no more than 50 and create if not existing:
- Click on Start, Run, Regedit
- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
- Click Edit, point to New, and then click DWORD Value.
- Type IRPStackSize , and then press ENTER to name the value. Use decimal values up to 50, 15 is default on XP.