If by freeze you mean it never comes back, upgrades are best left to after you fix the machine.
Most common cause is the lack of maintenance. Try this nice video -> http://reviews.cnet.com/4520-11319_7-6240575-1.html
Next is the old heatsink compound. It's about one dollar and if you maintain your own stuff, cheap fix.
PS. Reading http://wow.incgamers.com/forums/archive/index.php/t-397390.html I worry that if you should use this machine without repairs.
I have a Gateway GM5442 and need some advice on upgrades. I like to edit videos of a dance class I teach using Windows Live Movie Maker. The problem is that once I have a lot of clips strung together my computer starts freezing/glitching. I know that I can upgrade the RAM, but someone else also suggested a video card. I don't know anything about video cards.
Any suggestions? My computer hasn't been upgraded at all since I bought it, except for a WiFi adapter I installed, so it still has the factory specs.