32bit version of Vista can only see around 3GB from the 4GB available.

You may have a faulty RAM module in there causing the Blue Screen.

Try only leaving 1 module in at a time and loading into windows.

If 1 module causes a Blue screen and the other doesnt then you may have a faulty module.

You could also try downloading Memtest86. This can be booted from a CD and will check every bit of RAM in your laptop for any errors.