How To Reduce Physical Memory Usage

What can I do to lower the Physical Memory Usage in my Laptop?

For information, I am using Windows Seven Ultimate (build 7600) with RAM 1 GB, Intel Core i3 M350 @ 2.27 GHz.

When I hit task manager, the Physical Memory:
Total : 941
Cached : 85
Available : 81
Free : 0

Physical Memory average 92% all the time (currently I am using Windows Classic for it is known as the simplest and lowest taking memory of windows setting). If I am using it in normal Windows Seven Aero Themes, my laptop has a big chance to go Blue Screen.

Yes, I gotta tell you that my laptop got Blue Screen suddenly after previous days I set administrator and user password in BIOS. I thought at that time it is just because of it, then after I reset it to default way (no password at all) the system is still has a big chance to go Blue Screen.

I have tried to clean up with Ccleaner, defrag all my disks, using spyware malware removal, and it give me no positive result at all. It is still always goes above 800MB Memory usage with Physical Memory average above 80% all the time.