they don't any either!!! I'm telling they have EXACTLY the same hardware, including HDDs. the only difference is that i'm using a SUPERTALENT 02 2GB DDR3 with XMP overclocked to 1389 MHz and they are using another brand with no XMP an clocked to 1372 MHz. i know all that 'cause i overclocked their PCs myself.
As far as I know, Windows Experience Index uses the lowest score to determine your overall score. In other words, WEI works under the assumption that the chain is only as strong as the weakest link. In your case, the graphics' subsystem is the weakest link, so your WEI matches your GPU's.
That said, if the graphics' subsystem is your weakest link, then your RAM shouldn't matter.
And if your friends' hardware really is exactly identical to yours (other than the RAM), then maybe there's a Window's Update (software patch) that changes the way WEI evaluates the Intel integrated GPU -- and either you or your friends have yet to apply that patch.
Dunno. Strange issue. Still, unless you have noticeable performance problems otherwise, I wouldn't worry too much about what the WEI tells you. If you have the time/inclination, you might run some other benchmarks and ask your friends to do the same, so you can compare notes. rgd1101 posted a good general computer-platform benchmark earlier in the thread. If you want to test the GPU, you can grab 3dMark from the same site (Futuremark).