Quake 2 can be played natively on OS's up to Windows 98.
If you want to play it on Win XP or later you will need the Berserker Quake 2 program files and there is also a high resolution texture pack.
The program files are here:
http://www.moddb.com/mods/berserkerquake2/downloads/berserkerquake2-138-full
The texture pack is here (go to the bottom of the page and download _BersPak1.pk2):
[http:// http://berserker.quakegate.ru/ http://berserker.quakegate.ru/]