I found this post on this site.
This is for the Costco Model.
Would the same RAM work for the Walmart Model??
"""""Here is the 2gb Crucial item that worked fine in my wife's Acer D255e-1428 (Costco-$299-$20=$279). Atom N570/1.66mhz - 250gb
CT1596442 2GB, 204-pin SODIMM - $25
Strange that this model number isn't to be found on the Acer website. Anyway, on this model, no need to remove any but the four screws marked DOOR under the keyboard. Once these screws are out, the case plate on the bottom can be pushed loose through the exposed hole on the inside. There's a little diagram molded to the case (under the KB) in case you don't immediately recognize the push-through hole.
As far as the keyboard release clips go, the leftmost one along the top and the one on the left edge do not depress (not spring-loaded, just lugs.) Don't keep pushing those...they don't move. Your model may differ. Once the others have been depressed, you can gently pull the case edges out along that corner so that the KB pops up from the last two lugs. There is enough upward tension on the KB that it pops up as soon as the lugs are released. I did not remove the KB cable; it's easy enough to do this leaving it attached.
The D255e booted right up, 2gb recognized, no need to enter BIOS. Seems a little bit faster booting, but that could be all in my mind. Windows Experience Rating doesn't identify RAM as a problem anyway. The low numbers 2.9 and 2.0 come from the GRAPHICS and GAMING GRAPHICS, which no one buys these cheap netbooks for anyway. They are basically email, Facebook, and casual browsing machines, with decent performance on Office productivity tasks (if you MUST.) The rest of the WERs are Processor 3.3, RAM 4.6, HD 5.7.
It's for my wife, who already has a recently built Sandy Bridge DT, so we'll wait to see how she uses this before considering upgrades to W7 full version and MS Office. My guess is it will be fine as it is for lounging on the sofa and for staying in touch when traveling.
Incidentally, I originally bought a slightly older model for myself from Costco, hoping it would be a good, portable writer, but I have huge paws and just couldn't get used to the wrist angles needed for the smaller KB, so I took it back and got a 14" HP laptop instead. I loved the machine for its size and battery life, but my ape hands just didn't fit the KB."""""