My NX7400 's performance dropped totally. The CPU is allways at 100%. The clock speeds is 166 MHz main and 999MHz for each core. Could it be that the cooling fan failed or should I try something else. It is the same for both XP and W7.

No, you can't, it's way too old and weak for that. Actually it's not even supported by 7 in any version.

The original CPU was 1200 Mhz, namely 12 times the 100 Mhz "clocking" supplied by the motherboard.
The new CPU is 1.53 Mhz, namely 11.5 times a 133 Mhz clocking, if the motherboard can supply that rate of clocking.

If your motherboard can only supply 100 Mhz clocking,
then the new CPU would run at 1150 Mhz (namely its 11.5 multiplier over the 100 Mhz clocking), i.e., slower than the original CPU.

Can you try the 1.2 processor in some other motherboard?
It's possible that you "killed" it, when you removed it,
or after you removed it, by giving it a static-electricity burst.

Do you have another processor that you can try in your motherboard?

What happens if you put the 1.53 processor into the motherboard?
Does it POST (Power On Self Test) ?

Maximum of 1 GB per slot.
Yes, you can buy DDR400, it will be underclocked by the motherboard to DDR266. If you want some extra performance you can go in the BIOS and lower the timings one unit.
Yes, they will work, but not very fast. They should be used only as a last option.

Nothing, first try the disk in a working pc & see if it auto-runs in windows,if it does then try a different ribbon cable on the cd drive. If it doesn't then the disk is dirty or damaged. Also, not accusing you but windows 2000 is probably the most burned copy of windows around. If this is the case, go to whoever you got the disk from & tell them to re-burn it at 4x if possible but no faster than 6x, then the disk will work. As far as the bus speed is concerned(the jumpers), if the processor is a 100mhz, that's all the faster it will operate. Especially on older pentiums,which it sounds like you have. Now the processors will go to a slower speed, like 166 to 100. Keep in mind when switching cpu's you must set the jumper to the matching or slower speed or it will not post. Also, that speed is half what the actual clock is, meaning, 100 is 200,133 is 266, & 166 is 333 mhz. So if it's a socket 7 or 380 board, you can run an AMD or Cyrix cpu instead of the pentium & use whatever speed you'ld like because AMD products back then didn't lock the multipliers. Also on those older boards, some won't run certain ram speeds, like if the board has 100mhz ram it may not like 133 much. Ram wasn't very backward compatible back then.

Go to this link:

http://us.msi.com/?func=searchresult&keywords=ms-7025

Select the model motherboard you have and click on the CPU support link, it will show you a list of CPU's that are supported. You have a socket 939 board and AMD CPU's are now AM2, AM2+ and AM3 socket, which are 940 pin. It may be difficult to find a new CPU for your motherboard that is new since they have not been made in awhile.

Here's a little history
http://compreviews.about.com/cs/pchardwarebasics/a/aaBIOS.htm

More advanced stuff
http://compreviews.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=compreviews&cdn=compute&tm=128&gps=215_11_1267_540&f=00&su=p284.9.336.ip_p504.1.336.ip_&tt=2&bt=0&bts=0&zu=http%3A//www.adriansrojakpot.com/Speed_Demonz/BIOS_Guide/BIOS_Guide_Index.htm

Some systems have "bottlenecks," where small overclocking of a component can help realize the full potential of another component to a greater percentage than the limiting hardware is overclocked. For instance, many motherboards with AMD Athlon 64 processors limit the speed of four units of RAM to 333 MHz. However, the memory speed is computed by dividing the processor speed (which is a base number times a CPU multiplier, for instance 1.8 GHz is most likely 9x200 MHz) by a fixed integer such that, at stock speeds, the RAM would run at a clock rate near 333 MHz. Manipulating elements of how the processor speed is set (usually lowering the multiplier), one can often overclock the processor a small amount, around 100-200 MHz (less than 10%), and gain a RAM clock rate of 400 MHz (20% increase), releasing the full potential of the RAM.

AMD also produced x86 designs which competed with Intel on performance rather than price. In January 2002 the Pentium 4 gained a lead in sales and AMD marketing responded by giving their processors numeric suffixes approximating the clock rate that an AMD Thunderbird (and by inference a Pentium processor) would need to give matching performance, openly undermining the "megahertz myth".

I don't believe that's going to work for you.

According to what I've read that machine won't support a CPU with a FSB higher than 533.

Hi Gerry,

The understanding of how this works will require some study on your part. This is because you would not have enough basic knowledge to understand any short answers, that someone might give.

Here are some resources for you to read so you will understand this subject.

http://computer.howstuffworks.com/motherboard4.htm

http://www.directron.com/fsbguide.html

http://en.wikipedia.org/wiki/Front_side_bus

I hope you will find the answers you are looking for here.
Good luck.

Go to page 33 in your manual, see DRAM Clock/Drive Control & press enter. You can tweak your memory to run faster however your manual suggest not too. Hate to see you burn it up. As you will see everything is set to Auto:
Max Memclock (Mhz) [Auto]
1T/2T Memory Timing [Auto]
CAS# latency (Tcl) [Auto]
When DDR Timing Setting by is set to Manual, use this item to set the DRAM frequency. Would be nice to have a side panel fan blowing on your memory.
Link to your board.: http://www.ecsusa.com/ECSWebSite/Products/ProductsDetail.aspx?detailid=455&DetailName=Specification&MenuID=1&LanID=9

Have you tried the 1gb in the motherboard on its own but in different slots. i.e try slot 1 then slot 2 then slot 3 and see if you still get beeps.