Hoping someone here can help me out

[Nakoa]

I've got a dell 5100 right now. When i start it up it always gives me the amount of system memory has changed screen. It randomly restarts, high stress, low stress, idle, it'll restart anytime. All the programs I run randomly restart, photoshop cs2, firefox, ff, anything. My power supply died out a while ago and replaced that, installed new ram a little before that as well. My task bar will randomly switch from the normal xp taskbar to the boxier windows style task bar too. Before my pc started randomly crashing it would give me constant messages that my network was disabled then enabled a couple seconds after as well. I've opened the case up and taken out the ram dusted it out with a gas duster and tried, no luck. Any clues?

 

[Arianelle]

Have you already attempted reformatting your HDD?