I tried to ADD two sticks of 1GB RAM each to my 32bit Windows XP system, it already had 640MB, 1 STICK 128MB, 1 stick 512MB, so, I slotted it in and clipped the latches, but about 20-30 seconds after Windows boots, there's anoise like a 'brrp' and the system freezes, no mouse movement, no nothing, I tried the four sticks in various configurations, including putting it back in how it was before I started and putting the largest stick in where the previously largest stick was (what I assume was slot 0) but the problem kept happening. The second or third time I was MOVING RAM, one of the latches broke, but I didn't use that slot the next few times and the problem continued. I went into the BIOS, but I didn't see anything pertaining to RAM in there. Is it possible I hit something and caused a serious problem?

System:
Motherboard: MSI MS-7191
Windows XP 32bit
RAM: 640MB initially, trying to add ANOTHER 2GB. All the RAM sticks are DDR PC3200.Dalta,

You should install memory with matching memory. Many motherboards are picky and cause intermittent problems when you mix brands or even different models of the same brand of memory. I would suggest removing the 128mb and the 512mb sticks. See if the issue still happens with only the NEW memory installed.Hi

With that m/board you need to install the 1gb modules either in the purple or green sockets NOT 1 in green 1  purple. If that still doesn't work try the M/board with 1 module of the original memory and see if it starts. If still no go then try the memory in each of the sockets, and  hope that 1 combination works. When installing memory it is important to turn the power off at the wall wait a minute or 2 and then keep yourself grounded to the case as you handle the memory. Try not to touch the contacts as oil from your skin will cause corrosion. 

Keep us posted how you go

Lisa