Here's a handy command for allowing access to a permission restricted folder on XP Home:
cacls dir /e /c /g everyone:f
(where dir is the folder to target)
QuickBooks failed to install on a PC because of some restriction on a folder in the "All Users" folder. After making the correction, it appeared as though the permission had been removed by the loss of any users (or groups) that had been listed previously.
Everyone listing similar commands also mentioned to be careful with permissions because of potentially locking up your computer, but I didn't have any trouble.
( Win WinXP Windows XP Home Security Permissions )