So, my better half got me another gig of ram (1 DIMM). My already existing gig was in two DIMM's of 512MB. You know how a mobo has four slots, two blocks of two? Well, each block had one DIMM of 512MB and I was going to move the two 512MB DIMM's to one "block" and put the 1G DIMM in the other block leaving one slot open but alas, my viedo card was in the way of the clip and I was lazy so I just put the 1G DIMM into the spare bottom slot. My question is, does it make a difference? Would the RAM perform better if I put both 512MB DIMM's in the first block and the 1G DIMM in the second or doesnt it matter?

Shouldn't matter now (in this day and age).

The two blocks of two are generally configured for dual channel operation. The general idea is to have each 'block' set up identically - e.g. the 512+0, 512+0 that you had originally. So the ideal upgrade path would've meant getting two new, identical sticks and putting them in the empty slots (e.g. 512+1G, 512+1G).

 

In the bigger picture though, it's still a worthwhile upgrade you've gotten, so there's no real reason to worry about it.