I want to instal ram.my computer configuration is Pentium 4 1.7 GHz,RAM 128 mb,40 Gb HDD,windows XP professional sp2.I have three slots for ram.now only one slot is emplt.I want to increase my ram but the system is not accepting the change its not booting.the ram is not damaged.The system is accepting only two ram stics from any of the three i have.
when i start the system after installing the third ram it gives the error message

windows could not start because the following file is missing or corrupt:
system32\drivers\pci.sys.
you can attempt to repair this file by starting windows setup using the original setup cd-rom.
Select R at the first screen to start repair.

when i did it said
File setupdd.sys could not be loaded.The error code is 4
Setup cannot continue .press any key to exit.

Sorry to say you probably have RDram. From the wikipedia website.

The design of Rambus memory dictates that memory sticks be installed in sets of two. Any remaining open memory slots must be filled with CRIMMs. These sticks provide no extra memory, and only served to terminate the other slot.

http://en.wikipedia.org/wiki/RDRAM

SRX660

I thought i have sdram 1.33 MHz.Can you recomend me a free sofltawer which will tell which ram i have.

A good program called SIW will give you that information.

http://www.snapfiles.com/get/siw.html

SRX660