This is the first time I've heard about the path limitation under XP. But then again, most places I've worked for require the latest service packs of Windows always be installed. If that's a problem, perhaps you should check for the existence of the SP or such before you try setting it over the limit.
Another trick might be to figure out the short folder names (8.3 format) of the folder(s) used in the path and use that in the path variable. (The GetShortPathName
API could be used with the system plugin to get that info.)
Also make sure you use the large strings
version of NSIS to deal with strings longer than 1024 characters, or you may run into similar problems even on a "patched" version of windows.