Hey, guys...do you have to watch the 1960's series to understand the 2005 ones?

No not really, it helps if you want to understand more but you dont HAVE to watch the 60s Versions. But make sure you dont start watching a series really far on because then you will be Very confused.

It's not a must but it helps some. Having said that, There's some good episodes from the classic series I think you'd enjoy, particularly from the Tom Baker era. Check it out.

I don't really think you have to. I started watching some old episodes a few weeks back and to be honest I didn't enjoy it all that much.
You don't actually need it to see them to understand what's going on and the doctor don't really dwell on his past. So you might miss a few nod here and there but nothing major.

Nup. i started in 2005 when eccleston was the doctor

Dude, you don't even have to watch the 1960s episodes to understand the 1970s episodes. You can pretty much jump in anywhere.

Start from the beginning of the 2005 series - it's been designed so you can do that. There is no way you could go back and watch all of the classic Doctor Who - if you watched 3 Doctor Who episodes every single day, it would take you over 2 years to watch them all!