Building a budget PC need recommendations

RS 2013-11-15

I'm looking to build a small form factor PC for work to run SW 08

the OS will be Win7 and XP64 bit duel boot. I dont do much rendering and usually have less then 100 parts, however i do do simple simulations.

Could i please get some recommendation on a motherboard/ form factor/ CPU and graphics cards/ PCIE?

Looking to spend less than \$500 total build not including the OS.