What strength Power Supply Unit do I need for my computer? Possible freeze ups?

[K S]

Ok,

I want to know, what kind of PSU do I need?
How many watts?

This is what I have:

AMD 62x2 6000+
6 fans (1 CPU and 5 case)
1 DVD Rom
2x HDD
Nvidia GeForce 8600 GT (lower end one)
USB Printer, USB Keyboard
Foxconn 761GXM2MA Mobo
WIN XP PRO SP3

I dont know what my current power supply is - I havent found a sticker.

Sometimes when I plug a flash drive into the front USB I get a total freeze up. I have to access BIOS to set my SAMSUNG HDD as the boot drive. For some reason it resets.

So,

1) What power supply do I need?
2) Can the freeze up be caused by a power issue?