bsod when installing new 4gb ram

Ram should always be installed in matched pairs, 1 kit with 2 sticks are usually a matched pair. That does not mean that it can't be done, but if you want to avoid problems, use a matched pair. If you want to check the ram, I suggest running memtest86+. That is a excellent tutorial on how to run the test correctly.

As Essenbe says, matched pairs are best to avoid problems, but you can add more RAM to a system successfully IF you can match the specs of all the modules exactly.

There are 5 specs for RAM that must match:

• RAM Type: number of pins & design (like DIMM, SDRAM, or SODIMM for laptops) (must match)
• RAM Class: DDR, DDR2, DDR3 (can't mix and match here)
• RAM Voltage: (must match)
• ECC : with or without (must match)
• Buffering: buffered or unbuffered (must match)
• RAM speed: PCxxxx code or speed in MHz (should match but does not have to - all RAM will run at the lowest RAM speed spec, so you are just wasting money if you buy faster RAM.)
• Size (GB): does not need to match (but multi channel systems will run better if they do)

Any mismatched RAM in the specs above can result in system failure. (as can a defective module)
Check it!

please post your motherboard full name, the 4 gigs RAM stick may not work in older motherboards (like mine).

Uhm, How do you fit DDR 3 in DDR1 slots?

They aren't the same, here is a pic

What board do you have? I don't know of a board that will take DDR and DDR3 ram. It just won't fit.

Sounds an awful lot like mislabeled RAM to me. Makes me wonder if it is a "bargain" knock-off brand.

Please post the specs of the both sticks of RAM, including brand, so we can see. Indicate which stick was the original. And where you bought the new stuff from.