There were several different Dirty Pair series.  
The first (and best imo) was the TV series, it 
ran for 26 episodes.  Recently the series was 
released on DVD in Japan (Region 2 and no 
Subtitles) which I bought awhile back.  They did 
a really good job of cleaning up the picture 
quality (which if you've seen any of the fansubs 
of the TV you'll know the source for most of them 
was really poor).  There are plenty of scripts 
out there for the original TV series, so if you 
wanted to watch it the old school way with script 
in hand reading along with the video it's not too 
hard.  Cels from the TV can be a bit on the 
pricey side.  And since the show was done in 84' 
many cels are starting to show their age.

After the TV series there were the TV specials, 
which there were a few of.  And also accompanying 
were the 10 eps OVA series (which is what ADV had 
released).

Finally for what was considered the original 
Dirty Pair series was the movie, which I'm not 
sure if it's been released or not here 
domestically.  

After the original series came the Dirty Pair 
Flash series, which was 3 ova series of 5-6 
episodes each.  Though most of the characters are 
the same, their personalities change slighty as 
well as the character designs (which change 
drastically).