[Matrix510]

The actual limit on a 64 bit computer for RAM is either 72GB or 128GB (I do not remember the limit, but they have limited it for Windows even though it's capable of supporting more, I don't know why, nor do I remember where I read this)

But yeah, you could use 64 bit on that spec, meaning it would recognise more than 4GB RAM.

Although, I would honestly recommend upgrading that thing soon, Core 2 Duo's are ancient things.