upgrade

[dmt74]

I want to upgrade my current system and would like some feedback. I built it a couple years ago with a lot of help from some of the people here. My current system is as follows:
Soltek sl75frn2-L
AMD Athlon XP2500+ Barton core
Mushkin Dual Channel PC2700 dual channel 2x256mb ram
ATI Radeon 9500 pro
WD 80 gig HD
Liteon 16xDVD
Liteon 52x32x52 CDRW

I am thinking of just upgrading the ram to something like OCZ Platinum rev.2pc3200 1GB(2x512MB) dual channel or even possibly the 2GB dual channel (2x1GB)sticks. That might be a little overkill though.
I also want to swap my vid card for a eVGA E-Geforce 6600gt 128MB DDR3 AGP 8X card.

Hows this so far?

ok heres where it gets a little more complicated.
I had my whiz-kid nephew install windows xp pro on it after i put it all together and im pretty sure its not 100% legit so I want to buy a copy and not have to worry about it anymore. What is the best way to do this... can i just buy it for the key or do i need to reinstall it?
thanks

and Happy New Year!

[jayb1234]

For the OS install, boot from the new CD and do a repair installation. See this. Note that you don't want the recovery console option, but the setup option.

When it asks for the key, give it the new legal one.

After the install is done go to the windows update site and check for updates. You should be able to register and validate the key at that time. Your data should be safe, but it wouldn't hurt to backup anything important before you install the new copy.