I've been dealing with a half-baked Vista upgrade. Someone else went out an bought a copy of Vista Home Prem. and dropped it on a P4 1.8Ghz with only 512MB of RAM, and they all wondered why it got so slow compared to XP. Ha. Anyway, I went in and added a 1GB DIMM to upgrade to 1.5GB RAM and it started having random crashes. I ran memtest86+ on it and found RAM errors, so I swapped DIMM positions and the errors followed the location of the 1GB DIMM. Next step I did was put the DIMMs in my personal P4 machine and ran memtest96+ on there. No errors, on either single DIMM or both together. I went ahead and took the DIMM back to do a defective part swap at MicroCenter. Got the new DIMM in the 1.8 and it wouldn't even POST. I put the 1GB in my P4 and it's been runnign memtest86+ for the past half hour and and has made one full pass and then some. In the original system with the first 1GB DIMM it was spitting out at least 4-5 RAM errors per full pass.
I'm down to being suspect of the RAM controller capabilities of the i845 chipset. Anyone got much experience with upgrading them? This is a D845EBT board that works just fine with 512MB DIMMs, so far. I can let them run with 1GB (2x512) RAM but if there is someone who knows of another step to try, I'm all ears (er, eyes, on the web).