Cannot access any applications or internet

Hello,

Windows Vista home premium - Dell

My laptop computer was working perfectly until yesterday. I had access to all my applications, ie: documents, photos, Itunes, Windows live movie maker, etc. For some dumb reason I decided to backup my files (automatically saved to recovery E) and run a scan of my computer for any viruses. My internet connection was active at this time.
During the backup and scan I was presented with a few pop up screens which I don't remember exactly what they asked me (but it was something to do with protection) and each box that appeared made a recommendation, so I ticked what was recommended, I did this about 3 times. The backup had taken more than 2 hours and as I was in a hurry I stopped it midway. Then my computer appeared to be really slow so I rebooted. Suddenly, I no longer have any access to the internet. When I tried to access it a message pops up and states there is no internet connection as there is something wrong with the modem or server. When I click on the internet connection it quickly flicks to the connecting box but then it quickly disappears. so I can't even look at it to make any changes.
I can't open any of the applications mentioned above, in fact I can't open anything in windows or search the help area. Another error stated that : "Logon process has failed to create the security options dialog." Failure - security options.
I went to the help area to try to restore the back-up to what it was previously but it just doesn't allow me to as it won't go any further when I click on help. I'm not really sure what I did but all I know is that before the backup and before the scan and whatever I ticked has made it impossible for me to access anything on the laptop. If I could return it to the way it was before the scan and backup then I think it would fix the problem. Unfortunately, I'm not computer savvy and I'm not really sure what I ticked, I'm not even sure if this is the problem so I'm not sure which advice to take.
I also rebooted the computer about 8 more times but each time my computer became slower loggin in. Any help would be appreciated.
Noelle.