i recently installed a 512mb pc3200 DDR on my pc removing old 256mb pc2700 DDR. after installation my pc could only boot up until the boot screen appears then a blue screen error appears.

i've checked the memory card and i think it was seated correctly. i tried the memory card on other pc and it was working well so it could not be a bad stick.

heres the specs of my motherboard

ASROCK P4VT8

1. Socket 478 for Intel P4 processor
2. VIA PT800 chipset

* Supports Hyper-Threading Technology
* Hybrid Booster - a safe overclocking feature
* FSB 800MHz
* DDR 400/333/266
* ASROCK I/O Plus - supports up to 8 USB2.0 ports
* 1x AGP 8X, V1.5
* Serial ATA 1.5Gb/s, RAID 0,1,JBOD, SATA HDD HotPlug

What's the error message you recieve on the blue screen?
Does your pc emit a long beep or series of beeps when you turn it on with the new memory installed?
Might sound like a stupid question, but the Ram isn't DDR2 is it?
Have you tried running the two modules together?

its a ddr memory card, it doesnt give any beeping sound.... for the blue screen message ill write it up in my next post...

Remove the new ram card, dust out the slot, install the old card, see if you still get the blue screen, if you dont get this error any more, add the new card, if the error appears again, get the address and error. remove the old card, turn on, and see if you get a different address for the error, if you do, your new card is defective. Your main board supports pc 3200 and should time automatically, just to be sure reset the bios to factory defaults and save with the new card in slot 0.

here the blue screen error: after installing the new one...

page_fault_in_nonpage_area
....
technical information:

Stop: 0x00000050 (0xE7F7CD34,0X00000000,0X805C6EF2,0X00000001)

my pc still not running...

Here's a link to the error: http://aumha.org/a/stop.php#0x50

Try running the free program MemTest86 to test your RAM. Read the directions at this website in order to use it: http://www.memtest86.com/

make sure cas is set to auto in bios