How to set up registration thru email

My forum is continuously pounded by fake IDs and spam posts because I have not incorporated e-mail verification in the registration process.... Now I wish to include the same to raise the barrier for spammers... I checked the option "Verify Registration" in the Registration Tab....

Then it gives some SMTP related error which I forgot to note down... it was about smtp, port 25, set_ini() something.... (Sorry will post the exact error message, if required, cos now when I am trying to recreate the error, it says that I cant attempt to register for next one hour...!!)

Anyway, I dont have a SMTP server running on my PC and I dont think I'll run one.... I wish to use my existing gmail account to send the verification link to new users....

Can you please help me set up the entire thing from scratch...!! Sorry, but I really have no idea about php scripting and all.... So I would really need some basic help in setting it up...

Thanks and regards