What Win7 on my old pc

The purpose of the system is to play some old games

Not sure if the hardware is really up to that. A RAM upgrade would defiantly help as it would allow the games to have some more ram which might make them run better. With only 1GB, the majority is going to windows 7 itself

Mathii said:

The purpose of the system is to play some old games

In which case it may be better to run XP.
My nephew runs a bunch of older games on his 64-bit Windows 7 laptop, and he does run into a few compatibility issues

Don't even try 64 bit.

I'd google the model name and number + memory upgrade to see what your Upgrade options are. Run the Crucial System Scanner software to find out what type of memory is in your computer then google again the RAM specs given to see what kind of deals you can find on the web. Get at least 5-6 confirmations of the RAM specs starting with Crucial.

Sometimes it's faster and not muich more expensive to go to a parts desk at CompUSA or PCWorld to get the right RAM quicker.