Issues with my Acer Aspire M5640 desktop

Hi,
I have had my computer for just under 2 years and I'm having issues. I've paid so much money for techs to come out but no one seems to know what's wrong. I'm hoping someone on here can help. I'm desperate.
So what's happening is my computer often restarts whenever it wants, freezes alot and when I try to install a new operating system it comes up saying that there is no Cd/DVD driver.
I have wiped my computer over and over again, I've tried to install vista, xp and windows 7. I bought a new hard drive and done all possible updates for my drivers.
Please someone help me.
Thank you,
Clarissa

It sounds like a motherboard problem to me, or possibly an overheating processor or faulty ram, if it wont boot to cd and stay on, don't give up, try contacting a pc tech shop and let them see if it has a problem with an overheating processor, maybe it just needs the heatsink fins cleaned.

Did u install a new graphic card? Check u r system temp use speedfan software.also check u r cpu fan for dust.clean it if any.also please explain what u meant by 'wiped'

Check for overheating of your CPU heatsink. Make sure your CPU fan works normally. Reinsert the RAM sticks after cleaning.