Mysterious Virus? Registry Mechanic Fake?

You may have installed some other program that also installed the Ask toolbar and Registry Mechanic. It's called piggy-backing, it's not a virus or malware. The Ask toolbar is bundled with lot's of programs. It's how a lot of free softwares make money, companies pay them to install their toolbar or program also. You just need to be careful when you install something that you read the options for installation and deselect the piggy-backed program. Some softwares will install other programs without giving you the option to deselect and will not tell you they are also installing something else. An anti-virus program is not going to stop a bundled program from being installed if it's not malware.