I am sorry to say it, but with 4GB RAM and with a Q6600 Quad Core @ 2.4 GHz that performance is to be expected. CS5 is a 64 bit application and the more RAM you can throw at it, the better performance you'll get. If you put in 16GB in you computer you will see a great difference, but the Q6600 will still be an issue when it comes to performance when cutting HD footage with CS5.I am still having issues with that setup your recommending.
Windows 7
4 gig ram
Intel Quadcore 2.4 ghz
Nvidia GEforce 8600 512 mb ram (no mercury enabled)
Sata drives - 7200
All Scratch disks configured to drives that are not C:\
Realtime preview is stuttering, stopping and audio keeps going. Very confused here. CPU load seems low and ram has some to spare.
Am I missing something basic like not setting preview window to full?
/Roger