|Try following your own advice, afterall, you said it fixes 99% of all problems, lol.|
If I were you I would start by pulling my PC apart, clean every component (RAM, Heat Sinks, Fans, Graphics Card, the works). If you don't have a blower, then use a fine haired paint brush. Put your PC back together and make sure that everything is connected properly.
- Switch PC back on and check if the cleaning helped. If not;
- Try re-installing Windows. A fresh install of windows normally sorts 99% of your problems out.
Since it's "practically brand new", take it back or file a warranty claim. If you start poking around inside or wiping the OS, you'll most likely void the warranty, then she'll really be screwed. However, I find it hard to believe a system running a 5 yr old Celeron 430 is "practically brand new".