hard freeze prob. only when not logged into mmorpg in normal mode.

Ive been having computer issues lately and the main error is hard freezing. i fixed it a couple days ago and reformatted it (didnt need to, only needed to clean the dang heat sink.. lol) but now whenever i go into windows xp home ed. sp2, it freezes after 5 minutes if im not logged into my mmorpg (Trickster Online…. www.tricksteronline.com )

what could cause this and what can i do about it?
any help would be greatly appreciated!!!!