No, it wasn't the disk- just something that was hogging the complete system memory on start-up. My guru took it away, saved all my data, and reinstalled windows- I now have an ultra-clean machine- as fast and powerful as it used to be.
It's actually a good idea to carry out a complete reinstall from time to time- its amazing just how much clutter amasses over a few months to a year, depending on how much the computer is used (hevily, in my case!)
Just make ABSOLUTELY SURE that you carefully store all your original programme disks, and, just as importantly, your serial numbers, for future re-use, during a catastrophe such as this. I also store all my downloaded programmes a)in a separate folder (entitled Downloaded exe's), as well as b)saving them off the computer on a disk.
Thanks to all anyway.
Tosh