Computer blocked

[oxmord]

Hello , I'm not sure this is the right section to post this topic. I've got a phone call (British accent, U.S.number, allegedly an International Agency for fighting cyber crime). Have been told  that through my IP address are suspicious financial transactions going, and it's my duty to let them check it and allow them access to my computer for that.( Not this one, this is borrowed.) I've been so feeble-minded to do that.  I've never learned whether there are any such transactions, but have been offered an " absolute security program working lifelong on any computer" for only $499. When I wouldn't buy it, I'll be cut off from the World wide web.This time I've expressed my  meaning of this scam and interrupted the phone. Since that I never got into my Thinkpad, all of sudden it needs a password at start. I never had any such password at start, had only my mails secured with a password. My Thinkpad wasn't yet a year old and not quite cheap. Is there anything I could do to unblock it?

[AdvancedSetup]

If you let them onto your computer and they were able to set a password then it's quite possible you may not be able to get back into it. Is this a password at a Windows login screen or a black DOS box at first start of the computer? If its the black box when the computer first starts that's not good. If its just at the Windows login you may be able to get a local computer shop to help you get back in.