You can boot into a command prompt, then look for the mirc folder - usually c:\mirc. go there and delete mirc32.exe - that'll keep it from popping up the next time you run Windows. Then, from Windows, use Add/Remove Programs to remove it. (It won't be running since the .exe file is no longer there.)
Then, as Macondo said, clean your computer out.
Then run Spybot Search and Destroy all the time.
