I just built a computer myself on June. Windows 7's hardware test gave it 5.9 score and every thing over 3.3 should be able to run all Windows programs ( Hard drive was the slowest part. All the other parts got over 7 score).
What my computer has:
-Inter Core i5 750 processor
-MSI P55M-CD53 motherboard
- G.Skill 4GB Ram Dual Kit (with Ripjaws because they look better

)
- Asus Nvidia GeForce GTX 470
- Samsung 1TB hard-drive
- Samsung Blu-Ray drive
Then you also need ATX-chassis and maybe a power supply