Windows 7 wont boot with 4GB RAM

Try 1 stick at a time in each slot, you might find one stick to be faulty.

Sometimes swapping them round can make it work.

it's not the swapping them around that might make it work, it's the re-seating of the RAM that does it.
it's a troubleshooting step.

so your kinda correct but just a little vague.

Hi  

If you just added another 2 gb of ram, you DID check they were BOTH the same speed ???

All the best Brett  

+1

Silly question: X32 or X64?

shouldn't matter, not in this case.
this is a physical hardware issue, motherboard or RAM..

Just wanted to keep it simple!

true...