You have almost definitely caused your own problem by downloading a strange file onto your own computer. It may also be that someone else who uses your computer, such as a friend, family member, or colleague at work, has done this without being aware of it. Some recent viruses that distribute themselves using ***** programs such as Microsoft Outlook/Exchange also use mIRC and IRC to spread themselves. Well known examples of such viruses are the I LOVE YOU, SirCam, and Kle* viruses. Some viruses install mIRC somewhere on your computer and start it everytime you switch on your computer. A trojan/virus infection is not something you can solve simply by deleting some files or uninstalling mIRC. The trojan/virus will almost definitely have renamed all mIRC-related files, and will have hidden them in different folders on your computer, and will have installed other various files, and modified your system in other ways. The only way to solve your trojan/virus issue is to download anti-virus software, and if that doesn't work, you will need to contact an anti-virus company to ask for help. If they do not know about the trojan/virus, you will need to contact another anti-virus company until you find one that does. You will also need to change your attitude towards accepting strange files from the internet.