Getting SH3 to run on XP is almost a lost art anymore... The 4GigPatch can still work on the SH3.exe file, since all it does is inform the OS by a switch in the exe file's header that it can basically "flat address", which in Windows XP is 4 gig of RAM. So that is one requirement, that you have at least four gig of RAM in your system. You then have to edit the Windows XP Boot.ini file in the root drive to add the /3gig switch to it. Refer to AutoDesk's
How to enable the 3GB switch in Windows article, about halfway down the page. This does not guarentee success though. Since XP is 32-bit, and all apps running on it are 32-bit, they all share the same address space. All you are doing is asking Windows to give up a gig of its system address area and share it with the other apps. In other words, you still want to eliminate as much background stuff running, such as unneeded processes in the systray. You still might not manage to get it to run. The widescreen utilities seem to mess with the WinXP config somehow, and I have not been successful getting one to run yet. i can get stock 4:3 SH3 to run, but not with a widescreen lately...