Need help upgrading my computer

Forgot to say its currently running on Windows XP but I do have access to a copy of Windows 7.

Your current PC exceeds the minimum requirements (but not by a lot). So, technically you don't need to spend any money if you want to play the game. You may even want to wait until you have the game and see if you are happy with the graphical quality. If you aren't then you can upgrade.

The cheapest and probably most effective cost effective upgrade would be to upgrade the GPU. You could go up to a Radeon 6870 for ~$150 - http://www.newegg.com/Product/Product.aspx?Item=N82E168...

ASUS Maximus IV Gene-Z LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard $169.99

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Intel Core i3-2100 Sandy Bridge 3.1GHz 2 x 256KB L2 Cache 3MB L3 Cache LGA 1155 65W Dual-Core Desktop Processor BX80623I32100 $124.99

http://www.newegg.com/Product/Product.aspx?Item=N82E168....

CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1866 (PC3 15000) Desktop Memory Model CMZ8GX3M2A1866C9R $79.99

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

EVGA SuperClocked 01G-P3-1557-KR GeForce GTX 550 Ti (Fermi) 1GB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card $159.99 and a $20 rebate.

http://www.newegg.com/Product/Product.aspx?Item=N82E168....

This comes to $535 and if you can swing it I think this will get you almost to a whole new computer. If you need to not go over $500 then sbstitute for this MB.

ASUS P8Z68-V LE LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS $132.99

http://www.newegg.com/Product/Product.aspx?Item=N82E168....