Help! My Toshiba Laptop isnt working D:

Hello,

A couple months ago i got a toshiba portege m700, with windows XP
ive downloaded a couple instant messagers, but thats all.
for some reason a couple days ago, my computer started fritzing on me
it will freeze on startup and shut down
it wont satop sending me spam and pop ups
and it says that im connected to the internet, yet my internet browser says otherwise

does anybody have any solutions to my problem?