Dell Dimension 4400 Boot Failure error

I recently was working on a Dell Dimension 4400 and was adding more ram. I took the usual precautions before touching anything... I added another stick of ram which matched up with the one already in the pc. When I went to restart I get an error message that says.... Boot Failure: System Halted.... Now I can get to bios screen but it wont boot up.... Ive read and have been told I possibly blew the mother board. Any suggestions or help would be appreciated. Thanx

 

Enter the BIOS and go to hardware monitor, and report back your temps and voltages.

thankyou

 

Ok.. 2 things I tried on advice from other threads I found on the same subject and same pc. I put in a WIN XP Pro disk and it went through the boot sequence from the cd and ready to install... I pulled the old hd out and put in one I knew was working and it gave me the prompts to choose windows xp and to run in the different safe modes or start normally... but it wont go further than that. It keeps cycling the same thing... If i choose to start normally it goes back to the first screen whyere it gives the options to choose which operating system and then goes to the start windows normally or all the safe mode options.... and it switched back and forth between those 2. So now im even more confused ????