Hi;
Slow motion is not trivial. You must start with footage that contains enough information to slow down.
Here is a thread you might find interesting:
http://forums.creativecow.net/thread/298/702
BTW, I had a CX150 at one time. Cool little cam.
Steve
Win7 Pro X64 on Dell T3400 MultiTB SATA 8 GB RAM Vegas 10e x64 DVDA 5.2 Sony HDR-CX550V