My current RAM is 2GB and I upgraded it to 6 GB. I bought a 4GB upgrade, but apparently they are of different types:
My original one is 2GB PC-8500 and the upgrade is 4GB PC-10600.
Is there any effect if I use different types like that?
Both memories will work as the lower one. I mean, even having a PC-8500 and a PC-10600 both of them will work as PC-8500. This happends due to the fact that the controler can't deal with two different memmories with different accessing times.
According to a wikipedia article:
Both of your memories will work with 533Mhz.
This will only work if both modules are DDR3 RAM. There are DDR2 PC2-8500 modules as well as DDR3 PC2-8500 modules, but only DDR3 PC3-10600 modules. If you combine DDR2 and DDR3 RAM you will damage your motherboard and/or the RAM. (if you can fit the modules into the slots).
If they both are DDR3 RAM the faster one will clock down to the speed of the slower one.
Additionally your operating system and your hardware (CPU and mainboard) may not support the full amount of memory you are adding. A 32-bit OS will support only to a maximum of 4GB, some mainboards will have even lower limits.