mpg recording with Mercury TV tuner card

Hi,

I record programs on cable using my internal Mercury TV (the one that comes with a remote & FM). The problem is that before I start ripping it to DivX format, I want to edit the mpgs to remove the ads. The problem is that I can’t seem to use any mpg or video file cutter to cut these mpg files that are being recorded. I can cut the files using the Windows Media Editor but I don’t want to make .wmv files. Pls advise on where to get software that can be used to cut such types of mpg files.