I know, some of you've likely answered this one a hundred times.
 Here's the rub....I have 2 identical Dell Inspiron 8100 laptops, with XP SP3 freshly loaded just recently, and both now give up the same pulsing too fast error in drivertest, and lose steps while running live.
But I used this same laptop years ago, for both this engraver and a full sized mill.  So I know the hardware is fine, it used to run drivertest in the green with System Excellent all the time.  I almost couldn't get it out of the green status, as I recall, except by specifying a really high pulse rate.

So I removed and reloaded the driver, - no help.  Tried the alternate special driver and rebooted, - no help.
Eliminated all the unnecessary windows and applications processes in winconfig that I felt comfortable doing - still no help. 
I have NO extra applications loaded or running.
DriverTest will run in the yellow, pulsing too fast about 80% of the time, then occasionally go green for a few seconds, and back to pulsing too fast,  yellow.

Any thoughts?
Thanks in advance.

All I can figure, thinking about this, is that EITHER Mach3 has changed somehow since the years' old version I used to run, or something in SP3 has changed.  Everything else here is the same from when it used to run fine.

I just found a list of things to try in the downloads section, lemme go try all that. I see I have done most of it but this thing seems so close to being right... it shouldn't take much to create enough headroom.

It could well be the driver has changed, there were a lot of alterations done to it a while back for spindle and threading, they may be affecting things.
Load an old version of Mach and see if it behaves, if it does then you will have to make the choice between getting a desktop computer and running the latest version or using the laptop and running an old version.
Hood

Ok I ran through almost all the suggestions in the tweaking list, now it seems stable, though neutered, That's fine though, it's a dedicated CNC laptop.
Staying 90% in the System Excellent and remaining 10% in System Stable, in the driver test ....
Hood, thanks again for quickly responding.
Lemme run some parts again tomorrow and see if we are still losing steps. I suspect all is well now.

Hopefully it will be fine
Hood

I finally had a chance to put some time on the engraving table.  This is an absolute quandary.
I totally neutered the laptop to rid of any effect on Mach3's use of the system.
I have it at 25k Hz, and despite all I have tried, can't get it to behave.
The driver test runs right up fine, into the green, say System Stable and a couple seconds more says System Excellent.
I stopped for a few weeks till I had time to go back and check all my driverand motor wiring, ensured it is all shielded and wired correctly.
What it is doing, is randomly getting buzzy, that is, I can hear it missing like every 3rd or 4th step when jogging, but sometimes it works glass smooth.
So I don't think it is anything in the wiring or drivers, or it would stay consistent, and it is affecting all 3 drives.
I am using 3 motor reputable microstepping drives, they seem to operate fine.
This was formerly a professional Visual engraving table, run by an MSDOS Visual app and a separate driver box,and it operated fine that way.
I changed it to add a full z axis and make it Mach 3 capable.

I checked the step and dir polarities, it just sits there and buzzes if I change those, so I guess they are correct.
I am not sure what to try now.  It's a quandary.  Thoughts?

PS I did notice in the diagnostics screen, over on the right side, there is a timing indicator, and I noticed it will jump up to around 24,300, then back down to near zero for awhile, then a second or 2 later up to say 350, then repeat.  Is this a sign of a problem?

Two options are get a desktop or an external controller, personally I would go both
Laptops are not supported officially by Artsoft unless using an external controller. There is a reason for that and you have seen that reason first hand
Hood

Got a cheap solution to recommend in an external controller?
I don't have the physical space for a desktop....

There is the PoKeys which I think is about the cheapest but not sure how well it works as I have not been keeping up to date on its progress as a controller. I think it is limited to 3 axis and 25KHz max pulse rate per axis. There are Ethernet and USB versions, Ethernet probably the better choice assuming your laptop has a network port. There is a PoKeys section on the forum so you could check that out.

The SmoothStepper is a common one and works very well, can control up to 6 axis and has a max pulse of 4MHz so thats plenty even for a servo system. It comes in USB or Ethernet versions and I would say Ethernet is the best one to go for, again assuming your laptop has Ethernet.

There is also the CSMIO/IP-M from CS-Lab which is probably about the same cost as an Ethernet  SmoothStepper, it is also Ethernet and has a max pulse of 125KHz which would be plenty for stepper systems and lower end servo systems. It is up to 4 axis  It has onboard analogue  for spindle control and analogue inputs for spindle or feed overrides  also it has differential step/dir and 24v Inputs and Outputs.

So really depends on your budget and what you are looking for, personally I would choose the CSMIO as 24v I/O and Differential Step/Dir is much more noise immune. All three should however work well and it just depends on your requirements which would suit you best.
Hood