How long this has been going on I don't know because I use my laptop most of the time. I have Windows Vista and I was planning to upgrade to Windows 7 and found that the computer was shut off... in booting up it stuck at a black screen, but I could see the cursor and move it just fine. I ran the system diagnostics and found no errors except in the memory tests. I did it 4 times and got 4 different tests that failed. My question is: do I need to switch out the memory or could this be a bug/Trojan related issue?