It depends a bit on what version of PC-cilling you have installed, but one program that works on most versions is Revo Uninstaller 1.83 which you can find <free> at
www.majorgeeks.com/Revo_Uninstaller_d5706.html.
Run it in Safe Mode.
Using a registry editor like RegCure or RegClean or RegCln, look for PC-cillin Antivirus instead of what you think is installed. Remove it while in Safe Mode.
Also worked for us: Panda Quick Remover Panda-Software (free)
Once it has expired, Trend Micro wants you to pay to have it removed... TrendMicro is not playing nice in that case. They do post "removal tools" on their web-site, but those tools do not work for everyone.
My best luck has come using RegClean by Juoni Viourio on the
www.majorgeeks.com... but it takes a working knowledge of registry edits... though this is a very simple version. You need to know what to look for... so you look for PC-cillin AntiVirus
Another is PC-cillin PatternFile 5.970.18.
PC-cilling is difficult to remove because the designers have installed four invisible files with what are called King O drivers... and if you do not know what to look for, and the removal tool doesn't know what to look for, it is difficult.
Also, if you get the correct version, the TrendMicro removal tool will do it... which you have to stumble around to find... at
http://www.trendmicro.com/download dcs.asp or similar.
This is a problem file set, as you can determine by doing a Gurgle search for "PC-cilling Removal Tool" or similar.