Help please, Norton Internet Security 2009 won't scan

I sure hope that someone can help me.  There is something really strange going on with my computer.  It has slowed down something terrible.  I have tried to run my norton but it won't run.  It'll do the updates but that's all.  I honestly can't remember what was done last that might have upset things here. Can anyone give me a suggestion as to what i should do.  I'm on dial up and I really don't want to have to re-install it unless that's my last resort.

 

Help please

 

Maddie50