In the Task Manager, the number next to the "System Idle Process" is up around the 90's, but my CPU usage is stable at around 5-15%. However, the large amount of clock cycles next to a normally silent process is unnerving me. I know it's a SYSTEM IDLE process, but my computer has been active for more then 2 hours. Any way to get those clock cycles down?

In a word. NO. Idle is OK. Playing to the angels Les Paul (1915-2009)

Idle is idle. What this number means is that these CPU cycles are available for other purposes. You want to see a high number next to this process. 95 to 97% is quite normal.

Whereas it may show system idle, it eats up 100% CPU and stops other applications functioning, and even when I do have others running, for example a scan, this process still runs and nearly 100% usage. This happens right after a fresh install... so that is not the case. It is not the indexing service as I do not have that installed. I have no bugs, or viruses or similar. This is very annoying as it grinds my computer to a halt, that plus the hard drive spinning up every so often for no real reason, and sounding like the cd or dvd at full kilter. No there is nothing in the DVD/CD bay. Can someone give me some decent advice please?

"Can someone give me some decent advice please" Yes, learn about computers. You want high numbers in the system idle process. The higher the number, the less other tasks are using the CPU. It's not "using" up CPU cycles. "plus the hard drive spinning up every so often for no real reason" The hard drive should be constantly spinning, it should never stop. If your hearing loud whinning noises then it's not your hard drive, perhaps you have a fan going out.

Have we got two posters here (the names certainly look different)? If so, the second poster should have started a new thread rather than confusing the issue even more. The original poster is talking about 5-15% CPU usage, the other one (#3) 100% CPU usage. What evidence has poster #3 which leads him/her to the belief that it is the system idle process which is causing the 100% CPU usage? some other bloke...