Ok , so ive had my PC for about a month now and everything has been going great, no real problems or anything ( just messy cables and dust

)
Now, ive decided i want to get DX10 for the newer games that are out such as UT3, Bioshock etc. all of which run flawlessy on my system with DX9 , maybe its time i upgraded to Vista?
I have a copy of Basic with an Upgrade disc to upgrade to , i think its premium, but i only have 2 Gb of Crucial Ballistix Memory . My question is should i Upgrade to Vista and if so get another 2 Gb which will keep my system running optimally with vista installed?
Mike.