It runs in windows, and is very accurate, you can choose ...
1. Test until 100% coverage (a quick test to make sure your RAM is functioning reasonably)
2. Test for 1 hour (this will catch virtually all errors in your memory)
3. Test overnight (why not be absolutely sure your RAM is good? )
overall I found this freeware program works very well, I was actually suprised at how accurate it was at error detection.