Cant enter sleep mode

I am having intermittent problems placing my laptop in sleep mode. I use the
machine daily and typically can sleep/ resume several times a day before the
machine locks with the fan spinning at full speed.

Typically on closing the lid, there is a lot of HD activity until sound card
is turned off (with a click) and the HD LED stops flickering as the machine
goes into sleep. Sometimes, the disk stops (there is no sound) but the LED
stays on, then within a few seconds the fan switches on and then revs up to
full speed (a stalled service using CPU at 100%??). Other times, the HD
activity stops and the machine just goes quiet before the fan starts.. I have
waited for the fan to stop for 10-15mins but the only way to stop it is to
switch off the machine and reboot.

The laptop is only a few months old and is running VISTA business fully
updated. There is nothing placed in the event log before the shutdown and
afterwards there are just entries saying the machine didn’t shutdown properly
but no reason is given.

Is there anyway to log what happens as the machine goes into sleep?

The machine as office 2003+firefox 2+Nero 8+ acrobat 8+skype 3.6+winzip 11
installed on it