You might want to get something that watches after mIRC when your using it -
try bitdefender . Its freeware.

For your antivirus, theres Avast Antivirus and Avg Antivirus

I reccommend you get one of those. Since Trend Micro (pc-cillin) has a free online virus scanner, AVG can catch what PC-Cillin misses, and vice versa.

Online anti virus scanners-
Trend Micro (pc-cillin)
Bit Defender
Panda Active Scan