Oh oooo.....webinar ki tyaari ho rahi hai..
Yeah u can make ur system as a server and allow n number system to access it(with limited rights).
There are many 3rd party tools to do that use citrixonline ,Showmypc, sVNC ,crossloop,yuuguu,Mikogo......there are many(searched first check for many things).......in today's era viruses are biz model they are freely replicated in freeware,shareware or antivirus and all stuff.....
Mingleview is free...at least when i had used it was.
I mentioned few...there are many, many with skype or chat facility,many with multiple user multiple access,many with multiple os support with multidevice support(like ur mobile)...yep u can access ur system using ur mobile...