After installing NIS2010, PC freeze under two senario:
1) PC idle for 10-20 min with or without screensaver
2) PC runs while NIS starts background scan
But NIS2009 works without any problem.
My laptop's configuration seems to fit into the NIS2010 system requirement:
Microsoft Windows Vista® (32-bit) Starter/Home Basic
Compaq Presario C700 Note Book PC
Intel Pentium DualCPU1.73GHz T2370
2.0GB of RAM
106 GB FREE hard disk space