Flickering cursor mystery

I have a Lenovo 3000 laptop, with Celeron 550 (2 GHz), 1 GB, 160 GB
etc.

In XP (and in Vista to some extent), the mouse pointer flickers quite
rapidly at boot time. This makes it difficult to find the cursor on
the screen. In Vista the flickering is observed, but the cursor can be
spotted.
Initially, I thought this could be because the CPU was getting fully
utilised due to programs loading at startup time. But a complete
reinstall did not remedy the situation.

The flickering sometimes seemed to somehow be linked to the HDD
activity LED, so I presumed that probably there is nothing much else
to do except wait.

Then, by chance, I discovered that pressing the ALT key immediately
stopped the flickering. No more linkage to CPU or HDD activity, even
at startup pressing the Alt key stopped the flickering.

This has led me to believe that this could be a keyboard issue, and
some rogue key is continuously depressed causing the mouse to flicker
- till interrupted by the Alt key. So far I have been unable to find
this key. It is not the normal letter and number keys, that is for
sure, since opening up notepad with the flickering cursor did not
produce any keyboad output. I would like to know if there is any
utility that displays the status of the keys on the keypad.

The culprit was Prnt Scr.

Couldn't find an app that could list the depressed key, but a Linux
live CD was helpful.