Subject: Is it possible for a 'retro' virus to spread modified DNA in the body?

I probably saw this on some dubbed american sci-fi series; but would it be that 
hard to modify a bacteriophage type cell that injects it's own DNA into cells 
to produce more of it's own virus so that "beneficial" DNA could be injected 
and reproduced instead?

Sort of like cures for genetic disorders.

Well, reminds me of "spiderman" to be honest - you know, "overnight" changes 
are impossible - but is there any method for mass-propagation of modified 
(good) DNA?

Sorry if this is a "out-of-this-world" question - but I saw a SEM of AIDS at 
work which is frightful to see, but couldn't that be used as some kind of a 
vector? (Well, other pictures of those "moon-lander" viruses are called to 
mind).

Thanks,

Amadeus

ps. sorry if my terminology is messed up - been a while since I did viruses!

Re: Is it possible for a 'retro' virus to spread modified DNA in the body?