Anyone give any advice on new pc?

Hi everyone, im sure there are plenty of threads already like this and if so im sorry but ive recently been looking for a new pc, seeing as mine struggles to play even the first sims game.

Anyway my budget can stretch to around £400 so im not expecting the best here, just something to play left 4 dead and fallout 3 reasonably well, anyway any help given is appreciated thanks.  

http://www.legitreviews.com/article/690/1/

http://www.xbitlabs.com/articles/video/display/powercolor-pcshd4670-512mb.html

http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/7611-asrock-p45-p43-based-motherboards-unveiled.html

http://www.cpu3d.com/news/4321-1/cpu3d-exclusive-gigabyte-ga-p43-ds3-motherboard/story.html

Good Luck

http://cgi.ebay.co.uk/Desktop-Gaming-PC-E2200-4GB-500GB-ATI-HD-4850_W0QQitemZ390011033463QQcmdZViewItemQQptZUK_Computing_DesktopPCs?hash=item390011033463&_trksid=p3286.c0.m14&_trkparms=66%3A3%7C65%3A2%7C39%3A1%7C240%3A1318

£400 excatly. Will max anything - 4850, 4gb's of RAM, 2.2ghz dual core, 500GB hard drive. Sorted =].