Hotmail sending contacts spam?

Hi, I was informed yesterday that my hotmail had sent spam messages to a selection of my contacts. I ran a couple of tests and everything came back clean. I used:

AVG Virus Scan
Ad-Aware spyware scan
Spybot Spyware scan
Windows defender scan

Im pretty strict with the sites that I go on and very rarely get viruses.
Again at 6am this morning my hotmail decided to send a lot of spam to certain people asking them to click on certain links. I ran all the above again and everything came back clean. A few days ago I also got a few random pop ups, but this only happend for arounbd 30minutes, then that all stopped

About 20minutes ago I got a phone call from somebody claiming to be microsoft saying I have a virus bla bla bla. I told them where to go and said id sort it myself.

I can reformat my laptop no problem but my girlfriend has a lot of Uni work on here that I dont want to lose, and until I see her, I dont want to reformat.

Does anybody know if what I have is a virus? or what, im not sure. So far the action ive take is change my hotmail password, and forget the details from my internet browser.

Thanks in advance