I have a problem with my computer, can someone help me please?

My pc is just not working good. The gadegt for the Avg in the right hand above doesn't wok either and keeps loading and saying :initializing" and it won't open. The AVG it self works but not the gadget. Another thing is that whenever i try to open something for example yahoo messenger or some other files like adobe reader and some other files, and tells me that (choose the program you want to use to open this) and last week it wasn't like this. Idk whats wrong. As you can see, I'm not a computer expert so i really need some help. I have my finals next week and i better fix my pc. THX and I'll really appreciated (=