Help. Ive just installed some new memory in my computer, and when a switch it on it starts loading up. It gets to the Windows loading sreeen then the monitor comes up saying 'no signal' yet the computer is still on and I think still loading. Any ideas?

Remove the new RAM. Is it OK now?

If so most likely incompatible or bad RAM.

No its still not working. The only way I can get into Windows without the monitor turning off is in VGA mode.

I would try uninstalling and then reinstalling your graphics drivers.