Laptop seems to freeze after boot up

I have a customers Toshiba Satellite A100, which has a 40GB hard drive, 1GB RAM and runs a 1.4GHZ Celeron CPU.  
After a normal boot up the laptop seems to freeze for upto half a minute.  It will then come back and allow me to click on the start button.
Then when I open up windows (say Windows explorer), it is as though the window goes into the background and I have to click on it a few times before it becomes active or click Alt-Tab to get it back to the foreground.  It is an odd issue that I have never seen before.  I re-installed XP Home o the machine with all relevant drivers and it still does it.  I even put another , bigger, hard drive in and installed Windows with no Toshiba drivers and it still does it.
It makes for a very frustrating session of use and sometimes freezes up to the point where I have to kill the power in order to reset.

Any ideas?
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Can you do a quick test:  stop the Windows Automatic Updates service.

Click Start > Run
Type 'net stop wuauserv' and click OK

A black box should pop up confirming that it is stopping the service.  

Does that make any difference?

To start the service again you can either reboot or:

Click Start > Run
Type 'net start wuauserv' and click OK

Obviously this isn't a cure but it might help to narrow down the issue.
check if your disk drive runs in DMA mode, not PIO in device manager >ide/atapi controllers>primary>properties>advanced tab
mbellettyAuthor Commented:
Thanks guys for yuor responses and assistance.  One thing I tried last night was to replace the USB powered wireless mouse that the client was using and low and behold the laptop started behaving.  I am testing it for longer periods now with a new wireless mouse, still usb powered, but it looks like it was a faulty wireless mouse and the problem is now resolved.  
It is interesting how some issues are resolved by things you would not expect.

Many Thanks for your help
PAQed with points refunded (250)

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