Ok, since nobody was willing to help, I had to dig it myself!
The problem was that ISO image I downloaded (via torrent) was probably corrupted. I redownloaded it, now from official Sun/Oracle site, downloaded md5 checksum files (which I didn't get when downloaded with torrent), burned image on a blank dvd and voila - Virutal PC successfully booted Solaris 10!
So, my recommendation to everyone experiencing similar problem - download iso from official Solaris website, avoid torrents! That's it... I posted response to my own question, cause it will probably be useful to someone else!
Cheers!
Kemal