computer under seige and feeling overwhelmed!

                 Last year I panicked and downloaded Smart Engine, a malware program. It tricked me into buying it by giving me reports of dangerous viruses and i fell for it. After i downloaded it, my computer hasnt been the same. It takes forever to log in and not every log in attempt is successful as i get a blue screen once in awhile. And sometimes, when im going to a certain webpage-whether it be wikipedia or foxnews-, i get redirected to a another webpage for no reason. After finding out that smart engine was a malware program, i bought norton hoping that it would remove smart engine. I dont know if it did because i still get bluescreens and it still takes me 10 minutes to log in. and my webpages still keep getting redirecte. And now im under attack by another malware program. Antimalware Doctor has snuck onto my computer and keeps barraging me with messages telling me to buy so i can rid of all the "nasty viruses and trojans" on my computer.Im not falling for it again but i cant seem to get rid of it. I even had norton do a scan and it didnt do anything! WHat do i do?! I miss the days when my computer started up nice and quickly without a prob and when i could surf the internet without fear. BTW i use a laptop with intel core and windows 7.I am not sure but its a dell and i got it last year during the summer. Also, ever since smart engine, i havent been able to get my built in camera on my laptop to work! i dont know if its related or anything. So anway, please help! should i find a repair shop somewhere? i am at lost.