What's different about Screensaver preview in Windows 8?
I've found the most common problems with moving code from Win 8 to Xp is permission and dependencies. Check that the files are not needing some weird permissions (not sure what permission the preview runs with) and that all dependencies are honoured (also their permissions).
If I remember right, all windows screen savers are just renamed exe files with command line arguments. Maybe try rename it and run it directly?
Check what version of the framework you are using and try to use the client profile if possible
Also Try this small workaround if helps:
In Windows Explorer Go to > Options > Change folder and search options then click on the View tab and uncheck the box that says Always show icons, never thumbnails.
I hope it should work.
Screensaver is executable file but with .scr extension
When preview dialog required - OS start such file with /p key.See also https://docs.microsoft.com/en-us/troubleshoot/windows/win32/screen-saver-command-line