Mixed brand memory in a Dell XPS?

We’ve recently inherited my late father-in-laws Dell XPS 435t/9000. I helped him spec it out years ago, and we settled on i7-920 supported by 9Gb of RAM in the triple-channel board. It is now running very slowly , which I attributed to the ton of random crap he’d installed plus a general lack of maintenance on a long-in-the-tooth install. So I figure I’ll just do a clean install of W7x64.

I opened it up to blow out the dust and check it over first. What do I find? Dell has two completely different brands of RAM populating the six slots. Three of them are Hynix HMT125U6BFR8C-G7 2GB modules, and the other three are Elpida EBJ10UE8BDF0-AE-F 1GB sticks. Both are 1066, running at 7-7-7.

Now, I was always of the impression that running to different brands of RAM like this was not at all advisable (though they are identical in specs). I honestly don’t have much experience here – I’ve always put matched sticks in any rig I ever built. Is this a “bad thing” which should be rectified, or should I just smile and nod, put the cover back on, and go about my reinstall?

-Tuthmose

Smile, nod and continue with the install. If the specs are the same, and you aren't experiencing BSOD's or the like you should be fine. If you are concerned, run a few passes of memtest.

Thanks for the reply. As I mentioned, the machine is slow and unresponsive, so I did consider that this might be a part of it, but it's probably just all the junk my father-in-law had loaded. If it still isn't running smoothly after a reinstall, I'll reexamine the memory and run some memtest, but otherwise I'll just leave it be.

Thanks again for the help,
-Tuthmose