C2D E6400 P5W - Strange Little Problem

I recently finished putting togethor my new beast and I have a strange little problem which I cannot solve and cannot find posted around the various forums.

When I boot up the PC everything goes well except I get a blank (black) screen for about 15 seconds after the Windows Splash finishes and the Desktop appears. The total boot up time is around 50 seconds. What is disturbing me is that this did not occur until several days after the machine was running and does not appear to be connected any specific changes.......although I thought it began after I tidied up the cables at the back of my desk and change around the various items which are plugged into the USB sockets...could it be a USB controller or Device ID thing..?

As much as it is not the end of the world....I spent a bit of cash and a nice quick boot up was on of my expectations.

I have used Autoruns to look through the start up and see if it is getting stuck on something and have disabled a few bits and pieces but can't find any obvious culprit.

I probably need to start again from scratch and see where I get to before it happens again....but s**t.... what a long process that will be.

Has anyone had a problem like this one ??

> Windows XP SP2
> ASUS P5W DH (Bios 1301)
> C2D E6400
> 2GB GSkill PC 6400 DDR2 800Mhz 4,4,4,12
> GF 7600GT
> 74GB Raptor
> 320 GB Barracuda
> Coolermaster 600W PS
> Lite On Burn All Combo Drive
> Lite On DVD Rom
> Floppy Card Reader Combo
> LianLi PC71 Mid Tower
> BenQ FP93GX 2ms LCD
> USB: MS Optical BT Desktop, ADSL, Logitech QC IM, HP DJ6210

Not OC.....yet