I have a very old Dell Dimension XPS T850r and would like to upgrade the RAM. It currently has 128 and can be upgraded to a maximum of 728. I looked up what type of RAM it needs. "This Machine can take ECC or non-ECC memory. When you mix ECC with non-ECC, the ECC function will be disabled." What's the difference between ECC or non-ECC memory and which one should I go with?

ECC is usually used in servers as it provides "error checking." Often, it is more expensive and slightly slower than it's non-ECC counterpart. I recommend you go with non-ECC. -Ryan Adams Free Computer Tips and more:http://RyanTAdams.com Paid Tech Support: Black Diamond

According to Crucial, your system uses PC133, up to 256MB per slot for a max of 768MB. http://www.crucial.com/store/listpa... Just a word of advice, make sure you get low density RAM. High density RAM won't work in that board. http://www.geeks.com/products_sc.as...

http://www.crucial.com/systemscanner/ Go to the above link it will download a small activeX control strobe your PC and tell you what memory modules you require. Dont bother with ECC on an old board like that. Its more money than what its worth. And ECC does parity error checking on the fly. It provides better high availability because of this an prevents erroneous errors in RAM and system crashes as a result of memory errors. You will only find ECC memory in servers more often than not.

Be very careful about relying on Dell's own specs. I have an older Dell Dimension 4300, and the manual says- in TWO places- that it can use either ECC or NON-ECC. I found a screamin' deal on ebay for two 512mb ecc sdam sticks (used-$13 incl. shipping), and they don't work.. Machine just beeps at me and won't boot... and for all you techie guys, there is no BIOS adjustment on this system for this either! You can still find non-ecc sticks cheap and I would stay safe and get those.

Thanks for the replies! Follow up question: Does it matter what brand I purchase and how much I pay? Crucial has the 256 RAM for $34.99 while Geeks has it for $9.50. Thanks in advance.

Usually not. -Ryan Adams Free Computer Tips and more:http://RyanTAdams.com Paid Tech Support: Black Diamond