Mixing different brands of ram?

Ok so I bought myself a computer for christmas and the girlfriend wants gift ideas ideas and I was thinking of an extra gig of ram or something.

I'm not sure the brand of the ram I'm getting but I know it's pc5300 667mhz.

I know some ram is better than other ram with regards to timings and all that but is it a good idea to buy a rnadom gig of ram in the same speed to add to my existing 2?

If the mobo is asus then mixing ram brands is a nightmare, if it's another make you may be ok.

Why is that just out of interest?

I think it's an Asrock conroe 1066 or something - is this a terrible board anyway?

I don't know the reason for it but I personally have had problems with mixed ram in an asus board and so have 2 of my friends.

Sorry, i have no idea about the asrock board as i believe its an intel board and im an amd user.

Personally...

If you are this worried about mixing ram, then simply install it and sit back and watch. If her ram boots with no glitches, then KEEP it and spend the $$$$$ to replace your crappy ram with the same type SHE bought for u.
This keeps you AND her from killing each other. Have fun!!