Thank you both, you are really kind.
I did as you said and googled some key words from the warning.
Here is what i managed to find as informative and helpful http://www.americanpendulum.com/en/2013/02/26/you-have-48-hours-to-pay-the-fine-virus/
Also after i read there are all kinds of simillar infections (including all ukash viruses) with just a different name i visited this page, as suggested, for help http://www.bleepingcomputer.com/forums/t/482031/fbi-virus-unlocking-your-pc-without-any-safe-mode/?hl=%2Bukash+%2Bvirus#entry3005935
It seems i'll have to start my computer in safe mode with networking and then download and install an antivirus tool to scan my pc. I will give it a try.
Thank you again for helping