Combining DVDs

I've got a movie thats about two and a half hours long. there's a CD1 and a CD2. i want to shrink it and put it all on to one DVD. What program should I use to combine the movie ?

once its combined, then do i shrink it ? Or should I shrink the two files first (CD1 and CD2)and then combine those ?

 

What are the formats of the two cds (e.g. avi, mpeg, video_ts folder)?

 

there both avi

 

You may encode with e.g. VSO DivxToDVD (free version), then burn with e.g. Nero Recode. If there's a need for compression, Recode would handle it:

http://www.afterdawn.com/software/video_software/video_encoders/vso_divxtodvd_free.cfm

Good luck!