Lots of different things you need to check, but it all comes down to what you feel comfertable doing.
Re-installing should always be considered a last resort, It might fix the problem for sure, but then you will never know what the problem was to begin with and when it happens again, which it will, you will again be unprepared.
People have brought up some good hardware issues that you need to affirm work.
1).What type of ram did you buy? Kingston Value ram? Or Accubyte 45 dollar mail in rebate on a 50 dollar purchase ram from best buy?
If you bought the accubyte ram, you can bet 80% of your problem exists there.
First thing you should do, is during the next blue screen WRITE down the exact error.
Things to check in the OS:
1).Verify Hard drives are NTFS file system and that the drives are healthy. Check this in computer management.
2).Verify there are no device conflicts in device manager.
3).Verify the newest Bios on Motherboard and graphics card.
4).Verify the newest video and motherboard drivers in Windows - NOT XP DRIVERS. If you are using Motherboard installed X drivers, intall Motherboad manufacturer SPECIFIC drivers.
5).Verify memory is fit snugly and video card fit snugly into thier designated slots.
6).In computer management, open Event viewer and take note of any warnings or errors.
Basically there is a HUGE amount of work you can do before you should ever have to re-format, but if you just want a cheap qucik fix, go ahead and try re-format, but don't get anrgy when you meet this same problem 2 months down the road.