Hello and welcome.
Video editing software is pretty much what the software does, whether it is sports or flowers. What you want to do can be achieved easily in Windows Movie Maker, which is already on a win xp computer.
The problem you may have is the capture of the footage from the DVR, depending on the output on the unit you may need a video capture card or box to get the footage in to the pc. I believe pinnacle studio has a version with a capture box included or look on the web at DAC100 and advc110. The advc110 is better but more money.