Don't use your laptop, which likely will not meet minimum requirements anyway. Continue your CS5 project on the machine you are currently using.
CS5 project files do open in CS4, relatively successfully. I wouldn't bounce back and forth between the two programs too often, though--you stand a pretty high chance of breaking the project with too many conversions. If you're doing it once or twice, you're probably OK; just make sure to back up your original project before doing anything.
If that doesn't work, you might also be able to export an AAF file from CS5 (Project > Export Project as AAF) and open that in CS4. Note that whichever method you use, if your edit is more complicated or uses a variety of effects, you're likely to not have everything make the trip.
Thanks for the feedback. As far as not using my laptop and only using my desktop, don't reply to a question if you don't have a constructive answer.
Obviously my laptop will not have the sufficient speed to run CS5 the way it is meant to run. The only reason I need to use the laptop is when I'm not near the desktop (on location and/or offsite) which makes only using the desktop irrelevant. My question was "could" I find a work around, so that I can keep a project going if I am unable to take advantage of my main desktop system. Colin, thanks for the feedback. That was the answer I "needed".