Surprisingly easy to fit.

SDRAM DIMMs
DIMMs (Dual In-line Memory Module) are 64 bit so you do not have to fit them in pairs, unlike EDO SIMMS which must be fitted in pairs. DIMMs tend to be fast 168 pin, 10ns SDRAM. 100MHz SDRAM DIMMS will work with motherboards supporting Pentium II and Pentium III 350Mhz and above CPUs. 133MHz DIMMs are suitable for Pentium III and K7 Athlon systems.
DDR SDRAM DIMMs
DDR stands for Double Data Rate. DDR DIMMs offer twice the bandwidth of normal SDRAM which means that they perform twice as fast. DDR DIMMs offer a great overall improvement to system performance. They are compatible with newer Pentium 4 and Athlon XP Motherboards.
RDRAM RIMMs
RDRAM RIMMs are specially designed to work with Pentium 4 systems. Operating at 800MHz or 1066MHz it is far faster than normal SDRAM. RIMMS are not backwards compatible with older systems and must be fitted in pairs.
EDO SIMMs
EDO RAM SIMMs are 72 pin SIMMs with an Extended Data Out channel suitable for older first generation Pentium systems. EDO RAM is not suitable for 486 (or earlier) machines. SIMMs tend to be 32 BIT, 72 pin, non parity with a 60ns access time. All Pentium PCs require SIMMs in pairs.
SODIMMs
SODIMMs are designed exclusively for laptop computers. 100% genuine Kingston SODIMMs that will operate in most laptops. Please see the manufacturer's handbook for compatibility before purchasing.