There have been many lawsuits because Dell computers were made badly with cheap components. There is currently a US Justice department investigation ongoing. Go to www.wsj.com and look up their issues.
Basically it is a cheap computer and you will find it is more cost effective assuming it is out of warranty to just buy a better brand like an Apple
Well there could be a few things that could be causing your Dell to shut down immediately upon start up. One thing could be a hard drive gone bad, a bad fan or motor, bad sector and even a virus. Your best bet would be to get it to a computer repair tech as soon as possible.