i usually download trialversions and i crack them .
but my antivirus detects these cracks as viruses .
but i havent faced a problem with my computer.
do u think these crack files pose a threat to the computer health

Yeah some do.

Aside from being illegal, using "cracks" from the internet is leaving yourself wide open for virus attacks.

Apart from firefox, using downloaded cracks is the most common reason for virus infections i have to deal with.

Personally i dont mind this. I like the idea that someone trying to cheat the programmers out of their money ends up with their computer infected.