It seems like a driver problem like damian is saying. Windows get corrupted easily with video drivers... I am running a 4 month old rigg and I got problems with my video drivers on Vista 64.
If I have to rule out something else, I would go with maybe your hard drive dropping after a few seconds of boot up.
Usually, memory never died, or in extremely rare causes. More than often, it's DOA or malfunctioning at day one and not after a while.