How do I do this w/ Windows Media file editing?

Hello all. I was not sure of where to post this, so I thought I'd try here first. I have a large number VHS tapes I recorded Drag Racing from years ago on. (TNN TV) I purchased a TV card and software that allows me to copy video from video cameras and VHS players. I'm using a USB interface that Pinnacle manufactures and it all works great.

Here is the my delimma, many of these VHS recordings have TV commercials and are in varying lengths time wise. The software allows you to set the length of time to stop as the recordings are transfered at the rate of playback. The software converts the recordings to a Windows Media file.

I would like to be able to edit out the commercials and "crop" the end so to speak since it is easier to let it record too long. What software might I use to edit a Windows Media file or what format should I convert the file to so I might edit these files? I'd bet I have something on one of my computers already. (An XP Pro and Vista Home Premium equipped units)