Dell XPS 210 Crashed hard drive wont work and ram wont work....Help

I was using the computer to check my e-mail. walked away and came back and the computer had gone down. Tried to restart  and nothing happened. Ordered a new hard drive and tried to install it but it won't load windows. Tried to check each memory stick to see if that was the problem and still nothing. I am running out of ideas of what it could be. I have also checked the error message though dell and it says to replace the hard drive which i have already done. I have had the computer for almost 2 years and have never encountered a problem like this with any computer for that matter... Can some one help me I don't want to go crazy trying to replace a whole bunh of parts.