I've got a feeling you're going to need new software. If you want to buy something, Vegas Studio (for SD only) or Vegas Platinum Studio (addds HDV support) are top notch programs at the lowest prices around. I've used Vegas Studio to speed up an hour of traffic & clouds to one minute, then used the video on a couple of cablecast productions. In Vegas, speeding up the video is done by changing the video's properties and you can only increase it by a factor of 4 at one time. So I had to render the 4x video & compress it by 4 again, and again and once again. So there is one option.
If this is something you'd like to try out, both the programs are available as free trials from Sony's web site. That way you can do what you want and still have the software to play with for 30 days. Good luck!