I just got the Sapphire Radeon 2900 Pro 1GB.  I installed the card and had some problems with Catalyst 7.10 but got them installed.  I see alot of people are overclocking the card using two 6 pin PCI-E connectors instead of the one 6 and one 8 pin power connector ATI suggests you use.  
 
I tried installing ATI Tool, as its the software I prefer, but it kept freezing.  It wouldn't read the core/mem clocks when first starting.  I tried ATI Tray Tools but when I tried to OC the card I got a mem dump.  I tried AMDGPUClockTool but when I try to clock the card it says Clock Settings Not Modified.  
 
I using Windows Vista Home Premium.  I have an Antec TruePower Trio 650w PSU.  It's on ATI's approved PSU list.  I'm at a loss why I can't clock this card.  Any help or suggestions would be greatly appreciated.  Thank you.

Nvm.  RivaTuner did the trick.  It's odd ATI Tool didn't work with this card but as long as I got it clocked I'm happy.  I got it up to 800 core/1000 mem.