How does it affect a laptops behaviour beside 2 diff types of RAM surrounded by it? I hold PCII-4200 &DDR2 surrounded by mine.?

Answer:

PC2-4200 is a type of DDR2 memory. Specifically, you enjoy DDR2-533, which is also known as PC-4200 or PC2-4200.
It does affect a laptop, but not for the better.

They function at duplicate pace.

Since one is better, it reduce its speed to match the other.

I hope this help.