Computer trouble with Adobe Premiere & Photoshop CS4

[monks19]

Hi, i have a problem with my computer when using adobe premiere & photoshop cs4. With premiere, when i'm doing video editing, i can't wath the video in the program. the image is always freezing on one only, but the sound is normal. Whith photoshop, everytime i open it, after 5 to 10 min., it's always freezing and it shut down by himself without warning or explanation.

I've been using cs4 for almost 2 years, now, without any kind of trouble. But since last october/november, i replaced my old graphic card (Nvidia Geforce 7600 gs) by a Ati Radeon hd 5450. i don't know if the trouble is related to that change.

here's what i have for computer (see the attachment)

hope that somebody can help me

[filmboss80]

1. What format is the video?
2. Does your computer system meet the minimum system requirements for Premiere CS4?
3. How good is the air flow inside your computer case?

[RabidDog]

Re-install OS and ALL SERVICE PACKS.

[ranchhand]

everytime i open it, after 5 to 10 min., it's always freezing and it shut down by himself without warning or explanation.

When is the last time you cleaned the dust, etc. out of your box and especially the CPU heatsink? I like to start with the easiest things first, and overheating will cause reboot/shutdown.