Hello guys, I get myself into a deep trouble but can't help.

I'm using Windows XP Professional dual boot with Slackware 10.1.

My hardware configuration before the problem was:

Intel Pentium III (735 MHz)
Maxtor 6E040L0 (40 GB)
SD-RAM (2 x 64 MB = 128 MB)
nVIDIA GeForce2 MX 400 (64 MB)

The both sides of the DIMM slots were filled with 64 MB SD-RAM each. The middle slot was empty. Recently I bought another SD-RAM of 128 MB. And naturally turned off the computer and switched off the power to add it. I put it in the middle slot and restarted the computer.

Logged on to Windows. As it should, a right-click to My Computer and left-click to Properties informs my Memory update satisfied. It shows up 256 MB of RAM. It's happy. I'm happy. But that's not where it ends up.

After upgrading,
1. My computer suddenly reboots without any kind of notifications.,
2. It suddenly becomes stunned and stops response completely,
3. Sometimes the lasting duration is one hour, sometimes the half often the double but the machine is not stable at all,
4. I installed the game "Sims 2" successfully with a double unsuccessful attempt against the conflicts.
5. Being detected as 256 MB of SD-RAM, the game goes smooth but breaks with the problem no. 1 I said.

For your information,
Reinstallation if OS's is not left unattempted but they don't really agree to co-operate with my SD-RAM upgrade - shuts the installation in the middle with a message of hardware conflict.

If it's a line-up problem you need these to solve:
If these are the slots [] [] []
There were filled before problem: [64] [] [64]
They are filled with the problem: [64] [128] [64]

Please help me

Some motherboard / RAM manufacturers are first class jerks and don't make their mobo / RAM to the 'standard', and thus you MUST buy the RAM your motherboard company 'approves'. Other times the, as an example, yahoo online store memeroy resellers (excluding enet, which has been excellent for me) sell you the RAM that flunked the QA.

A third problem may be that the board doesn't allow certain speeds of RAM to be mixed or only in limited quanities. ie, my mobo can handle three 333MHz chips, but only two 400MHz chips.

1) Try it with just the 128 for a while and see what happens
2) Note if your RAM is all the same speed (333Mhz, 400Mhz) and latency (CL2, CL2.5 , CL3) or not.
3) Note the manufacturer of both your mobo and RAM, cunsult their websites.
4) Check your BIOS for any memory related settings, if the speeds are different, make sure you underclock not overclock.

Most likely you'll need to buy another 128Mb the same model as the one you just bought and run both of those, discarding the 64Mbs. For future purchases, may I recommend newegg.com, monarchpc.com, enetshoponline.com, as they all have excellent prices, merchandise, and customer service. You can also check out pricewatch.com for searching for other resellers (note the rating, don't trust anyone below 90%).

As an addition to CoolAJ86's excellent advice:

Download and run http://www.memtest86.com/ from a bootable floppy or CD-ROM; You don't have to let it run forever, mem problems that cause noticible symptoms like what you are seeing usually fail before it gets past 10% overall complete. Try it with just the new stick, just the old sticks and with all 3. If it fails for the new stick by itself then you have bad or incompatable (with your motherboard) RAM, take it back. If it fails with just the mix of all 3 sticks, try changing the order they are installed to see if it's something in the way your board detects the RAM. If mixing the order doesn't work then yes, you will have to replace the old 64MB sticks with another 128MB stick that's preferrably a twin to the one you have now.

Your system/motherboard manual should have a section outlining any rules about how to add memory to the system. There are often restrictions along the lines of "all SIMMs/DIMMs must be the same size or 'speed'".

If there are only three slots, I'd try putting the 128MB board in the first slot or the last slot and keep the 64MB boards together (i.e., in slots 2-3 or slots 1-2). The memory slot configuration you described seems a bit odd but the motherboard documentation will tell you for certain. But... if the BIOS "sees" all the memory, I'd guess that the way you have installed is okay. (It just seems a bit odd. Get it? three slots? odd? [ groan ])

One thing you could try is to pull out all the memory and test it, one board at a time, using memtest86. It's possible that one of the boards is going bad. The Slackware CD might have a copy of memtest86 on it. If not, you can get an older version that still fits on a floppy and run the tests after booting from the floppy. The newer version is too large for a floppy and the older version should work well enough to tell you whether you have a bad memory board. BTW, the official Memtest web site doesn't seem to have floppy images for the older versions any more. Try Googling for "memtest". That's where I found a floppy-based version for a friend.

Just a reminder: Do watch out for static discharge. (Got a wrist-strap?) Power completely down, pull the plug from the back of the system, etc., to avoid zapping something.

And good luck...

I tried 128 - 64 - 64 - and it worked!