Do I need more power? or a new motherboard? HELP!

OK here is the deal I hope you guys can help me out.

My system specs are as follows :

ABIT BH6/PIII-850MHZ/384MB PC100 RAM
Hercules G-FORCE II ULTRA 64MB DDR
Adaptec 29160 Ultra-160/ 18.4 Seagate Cheetah 15,000rpm
Plextor UltraPlexWide 40X/ Plextor 12x4x32 CDRW
Linksys 10/100 Eithernet Card
Soundblaster Live Value

Lots of fans, full height case, with power-man 300-watt power supply.

The PROBLEM , read carefully. The machine worked fine when I had a Adaptec AHA-2940U2W and a 10,000 rpm Ultra-2 Cheetah hard drive. Recently I sold the controller and hard drive, and upgraded to a 15,000rpm Cheetah drive and a new Adaptec 29160 controller to go with it.

Every since I added new 15,000rpm drive and new 29160 controller I have been having a problem I cannot figure out.

Evertime I go into my favorite game Half-Life my system locks up. I get total BLACK screen, and it looks as if the monitor was turned off. I have to HARD RESET to get back to windows.

When in windows everthing is fine, but whenever I switch into a OpenGL game, my system locks. Now I never had this problem when I had the old Ultra-2 10,000 rpm cheetah hard drive, and the old adaptec AHA-2940U2W controller.

I tryed re-installing the OS lots of times, and still same problems.

NOW HERE IS THE WEIRD PART!! When I take out the G-FORCE II ULTRA and replace it with my older Viper 770 Ultra "TNT-2 ULTRA" my system runs fine. I can play all my games and never have any problems.

DO YOU THINK THE NEWER HARD DRIVE AND CONTROLLER ARE TAKING MORE POWER, AND BECAUSE I HAVE A CHEAPO 300 WATT POWER SUPPLY I AM RUNNING OUT OF POWER? WHAT ELSE COULD IT BE?

If I pop in a good name brand 400 watt power supply do you think I will be OK?? Or do you think I might have some sort of motherboard problem? Remember the G-FORCE II ULTRA WORKED FINE IN THIS BOARD, UNTIL I REPLACED THE HARD DRIVE WITH A NEWER FASTER ONE, AND REPLACED THE HARD DRIVE CONTROLLER.

Please give me your opinion on this! ALSO!! I tryed the video card in a one of those new Compaq computers and it worked fine, so I don't think it was the card, although the damm card runs super hot even when the case is open.