Tune up kits

I've noticed you can buy tune-up kits with MB / Chip / Graphics Card that are pretty cheap. I wondered if you can use something like this to fix up an old OEM computer and whether there are any compatibility issues I would need to look for? For instance, will all RAM work with all MBs? Will I have problems installing my XP that was on a different MB before and, if so, can I get a new validation code?

 

As far as the RAM portion, you will have to have the type that is compatible with the motherboard. All are not alike, as far as speed, density, etc.
I believe you will need to get a new activation key code, due to this "project" would look like a brand new machine to MS.
I'm sure someone will correct me if I'm mistaken, but I believe thats how it works.

 

I didn't think about the RAM. Thanks.