memory - Laptop RAM upgrade - 266mhz or 533? PC2-4300 or 4200?

I want to upgrade the RAM in a Toshiba Satellite M70 SR3 Laptop.
SIW diagnostic software gives me the follwing info about the current RAM:
Capacity: 512MB; Type: DDR2 (PC2-4300); Speed: 266Mhz (DDR2 533); Supported Frequencies: 200.0 MHz, 266.7 MHz, 266.7 MHz.

The CPU is an Intel Pentium M 740, and the FSB speed is 532.0 MHz

I've been looking for replacement RAM (2x1GB), but the specs never seem to match exactly.

Is PC2-4300 the same as 4200? I read one forum post that said they're interchangeable. Often the speed on PC2-4300 or 4200 RAM is listed as 533Mhz. Some references say that a listed RAM speed of 266Mhz mneans an "actual" speed of 533Mhz, which is confusing. Is that what the "DDR2 533" in the specs means?

Will I be able to install 533Mhz RAM? Does the fact that the motherboard FSB is 533 Mhz matter?

Any and all replies welcome.

Thanks