With the 'boot from cd screen and not go further'
problem after you put a new RAM module in your PC, you probably only needed to change the boot order of storage devices in your BIOS setting, or cleared your CMOS chip of the BIOS, and not reformat the system. Though, I wouldn't of thought re-installing the OS would have fixed the problem.
Anways, about your display being all choppy...because you've reformated and installed a fresh copy of Windows XP your system doesn't have the drivers installed your your specific hardware, which includes your Graphics Card. Windows XP is currently using the generic display drivers.
To fix the problem, simply go to http://www.nvidia.com
and download the forceware display drivers for your GeForce MX4000 Graphics Card. Once you've installed the drivers, go to display settings and set your monitor's refresh rate and resolution to the optimal settings.
You should also download and install the latest chipset drivers from the vendors website and audio drivers for your soundcard (if you have a PCI soundcard). If you have onboard audio, audio drivers are usually included with the chipset drivers for your motherboard.