Start by scanning your computer for spyware and viruses. Follow the beginning instructions in the Security forum and if you've been infected, post your follow up questions there. You description is a common symptom of spyware.

Restore the previous backup point

Erm- no.

If the last restore point contained components of malware programs, going back to that point willl just bring that malware back in to your system.

I have scanned for viruses and spyware and nothing is detected. I also get another window that is saying that part of an "n-case" file was removed without my consent and it gives me 3 options, remind me later, uninstall the rest, or download it all. I always hit remind me later but I tried to download the rest and it still appears. We took the computer to a shop and we got a new harddrive and the power switch was fixed and they said its a good running machine. Its an emac and they told us that they are only made for use up to a year and we have had it for 4. Do u think its time for a new one?

n-case is definitely an "unwanted guest" that didn't get fully removed; did you make sure to install the latest virus/spyware definition updates for your utilities before you ran them?

Your computer is probably fine, even if it is a bit old. Given the existence of n-case and the rundll error, I'd say your problems are just the result of spyware, so I'm moving this to our Security forum. Have a read through the thread there for suggestions on removing persistent spyware elelments. If nothing seems to work, download HijackThis (the link to the download site is in my sig below), have it scan your system, and post the contents of the log file it generates.