[3ventic]

You shouldn't need to change compatibility mode. Just make sure "Run as administrator" is ticked in both samp.exe and gta_sa.exe properties, under compatibility tab. If it doesn't work, delete/rename gta_sa.set in your documents/gta san andreas user files and/or rename your GTA directory.

I'm running samp without compatibility mode on Windows 8 Pro 64-bit.