Since my post in February I have been wondering just why my Dell Inspiron (cheap but good spec) Laptop did not work well with Mach3 whereas an old (low spec) desktop worked so well. The answer has been found in the posting by 'DaveC' at :-
http://www.machsupport.com/forum/index.php/topic,3378.0.html.
An extract from his post is as follows :-
The secret is .... disable the ACPI driver!
Open the device manager and find the 'Computer' icon.
Click on the plus next to that and you will see something like Advanced Configuration and Power Interface (ACPI) computer. Chose the 'update driver' option and select 'Standard PC' as a replacement.
Windows demands a reboot after this, and a lot of the hardware had to be 'rediscovered' and reinstalled (all used drivers it knew about already, so was painless), another reboot for good measure and now it works flawlessly.Thanks to DaveC my Dell Inspiron now works beautifully with Mach3 and I have every confidence it will solve all the issues mentioned by others (unfortunately not Dave's latitude D800 it would seem) in the above posts.
Tweakie.