Marathon Games for PC?

Can you you suggest me some games that are good for a 6-12 hours of marathon gaming. I want to sit with a friend and play or beat a game in that amount of time. Something like BioShock, Half Life 1, Jazz Jack Rabbit, Lost Vikings. Those are the game that I think are good for "marathoning" :) . Thank you in advance!

P.S. I have a C2D 6400, 1GB 800Mhz Ram, GF8800GTS 640, and Windows Vista. I think only Vista will be the problem because I like playing old games too. I preffer retro games...

yeah, escape from butcher bay is perfect for this - it's about seven hours long, and it's gaming heaven the whole way through

if you enjoyed bioshock, try and find a copy of system shock 2 as well, it's more or less the same, only way better

metal gear solid 1 and 2 are both about the right length for a marathon run through, too

f.e.a.r is worth a solid play as well, as are the max payne games

i can't think of too many others that are worth playing all the way through in one sitting, it's pretty subjective too, since all linear games are marathonable, really