Not too picky about the type of game, it just must be:
Low PC requirements
2D graphics (or simple, basic 3D)
and able to be played in a window

Games I have already tried:
Conquer Online (would prefer something similar to this)
Runescape
Eudemons Online
Maple Story

If it doesn't fit ALL the requirements, feel free to post it anyway, I may consider it. Also, I liked the quick style of Conquer online. Most mmorpgs I have played seem very slow in comparison. I was hoping to find something quick like that too. Thanks in advance.

Have you tried Puzzle Pirates? Been playing it for two years now. At first it was a little overwelming but then it was great fun and you get addicted really fast!

lol low req get a new comp geez.

Trickster,I can run it whit a laptop(not powerful at all),so i guess it's ok:
http://www.tricksteronline.com/
And Gost online,not sure if you can ru it in window mode though:
http://go.gameflier.com.my/

Try NEaB (http://www.nowhere-else.org/).

It's 2D, browser-based (runs on Java), and has a decentish community (the community used to be better, though :|).

KoL (http://www.kingdomofloathing.com) is also pretty funny the first time around, if you don't mind the stick man graphics. After you "Ascend", though, it gets pretty redundant.