GA-965P-S3 memory problems

I had 2GB in my computer (2x 1GB), then I decided to add 4GB (2x 2GB), but when I added the chips it wouldn't start. I replaced the 1GB chips for the 2GB ones and it works, I also tried adding 1 GB chip to the 2x 2GB and nothing. It's either 2x1 or 2x2. I updated BIOS to F13 but still same problem.
The 1GB chips are Patriot DII800 (PSD21G8002) and the 2GB chips are Samsung 2GB DDR2800 (MM-2GBPC2800S).
Did I do something wrong?

The 2gb one:
General
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Samsung (CE00000000000000)
Size 2048 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number M3 78T5663QZ3-CF7
Serial number 42511DD9
Manufacturing date Week 52/Year 08

Attributes
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no

Timings table
Frequency (MHz) 266 333 400
CAS# 4.0 5.0 6.0
RAS# to CAS# delay 4 5 6
RAS# Precharge 4 5 6
TRAS 12 15 18
TRC 16 20 24


And for the 1GB:
DIMM #1

General
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) PDP Systems (7F7F7F7F7F020000)
Size 1024 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number PSD21G8002

Attributes
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no

Timings table
Frequency (MHz) 200 266 400
CAS# 3.0 4.0 5.0
RAS# to CAS# delay 3 4 5
RAS# Precharge 3 4 5
TRAS 8 11 16
TRC 11 14 21

It tries to start, the fans start but after like 1 second it shuts off and tries again and again and again, or, it starts with a continuous beep but nothing loads (nothing on the screen and no hard drive activity)

Dunno

Thanks, will try it when I get home. I didn't know anything about these timings you mentioned but started reading on it, and realized lower numbers are better, so if I manually change it to 6/6/6 would it be slower? What if I changed it to 266 MHz but 4/4/4/12? (both share a 266 4/4/4 setting, while the 2GB has 12 TRAS and the 1GB has 11 TRAS for 266MHz, so guess 12 should cover them?). Forgive me if I'm not making any sense, I'm just starting to learn about these things

Hmm... I'm not sure what happened. I changed it and the computer now starts up, and Windows XP comes up fine, but in my other partition with Windows 7, it hangs at the start (on the 'Starting Windows') screen. I wonder if it's because XP is not using the 2 1GB chips but Windows 7 (64 bit) is. I tried several settings but always the same thing.

Hmm... I looked and looked but couldn't find this setting in the BIOS anywhere (in advanced mode Ctrl-F1)

the motherboard supports up to 8GB. Windows 7 shows 4GB.
I guess I'll just leave it at 4, which is still double of what I had. If I ever want to upgrade from there I now know what to buy.
Thanks for your help though, I learned a lot!

hello, I have gigabyte motherboard GA-965P-S3, and the system worked fine when I had 1x1 GB ddr2 RAM, and when I add 2 gb ddr2 more computer turn on but can't boot. and when I add only 1 gb and 2 gb of ddr2 RAM it works fine again. How can I make my computer works with 1 gb more, I mean with 2gb and 1x1 gb