Urgent help with so called virus

Hello,
I have a serious problem with my computer.....I was downloading a program for special video effect form emule...I know this is very dangerous,but then I opened it and after that my comp restarted...before that all my music and pictures on disc D were there...the comp restarted and it had so called ''email-worm.JS.Gigger'' and it said I had to buy antivirus protection program 2010 or something...I didn't buy anything but all of my stuff from disc D have disappeared!!!...First it said ''disc D has to be formed/formated'' and if you click yes it says ''disc D can not be formed/formated...Are my stuff there deleted?..I removed this antivirus program and will get my computer cleaned,but will this retrieve my stuff from disc D?...How is it even possible,a ''virus'' like this can delete disc D?....I really need your help,thank you.