I have over 64MB of RAM, but DOS can't see it all while Windows can.

The way that DOS is designed, it cannot see over 64MB of RAM. Almost all of the time, though, any DOS program will not require any more than 64MB anyway. You can try to find a special memory manager, but the thing to do is get with the times and start using Windows.

There is 128KB or 384KB of RAM that is never reported when I boot up.

This is normal. Some BIOS versions do not show that area of memory right between conventional memory and extended memory.

My system seems to have slowed down upon adding more memory.

Well, first you need to make sure that all of the new memory is being recognized. Refer to the above question. If your memory upgrade took the system above 64MB of RAM and you have a chipset that doesn't allow cacheing above 64MB (such as the Intel VX, FX, and TX chipsets), then there isn't much you can do. Those chipsets cannot internally cache more than 64MB, so any memory above that mark will just slow down the system. also, check to see if the new memory you added is equivalent or faster than the old stuff. One common mistake is to install memory that is slower than what was already in there. This causes the system to reduce the OVERALL speed down to that of the slower memory. For example, installing -70 ns speed memory is a system that already had -60 ns memory will decrease the speed.

I am getting a memory parity error when I boot up.

• If it crashes as soon as you turn it on, you are probably trying to run non-parity memory in a parity system. Replace it.
• Make sure parity checking wasn't accidentally turned on in BIOS with non-parity memory in the slots.

I am getting parity errors during normal operation of the PC.

If you just get them every once in a while, i wouldn't fret over it. Sometimes little errors occur in memory. If you seem to be getting these associated with random lockups, I would check the rest of the system because many things could be bad. Sometimes improper cooling, for example, can cause random errors that may look like something else is awry. It is starts to happen a lot and these other things aren't a factor, then you probably need to replace your memory.

Installed Memory but Win XP Pro won't start now

Question:

I added 256mb to a computer with 128mb. The BIOS sees it but when Windows loads I get a blue screen.

Answer:

It is important that any new RAM module(s) be fully compatible with both the motherboard and/or any other RAM module(s) already in the system. Additionally, there are sometimes jumper switches on older motherboards that need to be reset for new RAM configurations. Consult your motherboard's manual or the manufacturer's web site for specific instructions and compatibility requirements.

If you do not have your computer's manual and the manufacturer doesn't provide a support web site, you can use Crucial Memory's web site to determine the correct RAM and capacity for your specific make and model computer and/or motherboard.

How to identify a bad memory module:

If you turn on your computer and you hear a series of beeps and the system will not boot, this behavior usually indicates a hardware problem.

The beeps that you hear are clues to what the problem could be. You can usually find this information at your manufacturer's website.

The most common problem that I have seen is either a bad memory module or memory that is not seated correctly. The first step is to unseat your memory modules, then reseat them. If this does not correct the problem and the beep code indicates a memory issue, then replacement would be your next step. If you have multiple memory modules, you can isolate which one is causing the trouble by completely removing one from the system. If the system boots fine, then the modules that are installed are good. Repeat this step until the system refuses to boot. Then you will have found the offending module.