XPS 720 RAM Issues

Hey guys

So recently I had issues installing a new version of XP Pro to a new HDD but that issue is fixed thank you to JackShack.

I had a problem before this that I decided to deal with after the HD & OS Install.

When I first got the computer it was from my best friend, he had told me the motherboard was shot because someone ran a ram test or something.   I am writing this on the computer he said the motherboard was gone so I doubt it is but I believe the RAM slots have issues.

 When I opened the case I did a good clean and took the ram out, I then put back in.  After I was done cleaning and everything I would plug the CPU in and this is what happens :

CPU Sounds very loud ( Initial boot up sound but lasts forever ) , My monitor does not react as if it stays in sleep mode but all my LEDs come on.  I get the illuminated lights 3 4 on the CPU and lead me to RAM.  I then ran tests pulling them all out and booting them with 1 at a time.  I seem to only have 1 stick out of the 4 that is operating on the 3rd and 4th ram slot on the mobo.  I have to switch at times when my power plug is disconnected and I plug it back in otherwise I get the same effect of loud noise and no monitor response.

This is extremely frustrating because I went from 4gb to 1gb.  If this is a slot issue then I would probably be better off finding 1 really good stick or 2 if the CPU will handle it.  The CPU will not handle all 4,3,or 2 at once it does the same thing.

I dont know if I should try running with 2 sticks in different slots but I am tired of messing with it atm.

Any insight much appreciated.