Don't know anything about win7...
But as far as Astropulse goes, there's only 32-bit applications available, even the optimized is only 32-bit for windows. For SETI_Enhanced there's also optimized 64-bit applications available. For both running optimized applications gives a big boost in speed, and is definitely the way to go.
With optimized applicatins, BOINC will only get work for whatever optimized applications you've got installed. For non-optimized, you'll get based on your preferences. Reasons to getting Astropulse even think this isn't selected can be, each Venue has separate settings and it's possible a computer is using a different venue than the other computers. Or, you've checked "if no work available, send work for other applications".
If you're running optimized applications, it's actually an advantage to run Astropulse, since it's "paying" more credit/hours than SETI_Enhanced does. But, being for a laptop that likely is on the road and often off and so on, only running SETI_Enhanced is still likely the best.