Late last week I started noticing a problem with my laptop, a Dell Studio Core 2 Duo running Windows Vista. The problem first manifested itself by my laptop’s fan cycling on and off quite often, accompanied by a shorter-than-normal battery life (about two hours as opposed to the 3 ½ to four hours when the battery was new). The battery is less than a year old, and I use it only when necessary, so it shouldn’t be having charge retention issues just quite yet.

I looked at the task manager, and noticed that CPU usage was staying steady between 30 and 40 percent even though I didn’t have any applications running. The disk activity light wasn’t active.  When I looked at the process list for all users, I found that the System Idle process was around 90 to 95 percent. I would think that the CPU usage plus the idle percentage would come close to 100%, so this concerned me.

My first thought was a (insert evil laugh here) virus, but every scan I did, including when running in safe mode, didn’t show any problems.  There also weren’t any significant errors (or as NASA likes to say “no unexpected errors”) in any of the logs.  I was flummoxed.

My next step was to run msconfig and stop anything that was not absolutely necessary from starting at boot time.  I also went through all the scheduled tasks, and either disabled unnecessary tasks or set them to run only when on AC power. I also paid close attention to the applications I was using when the problem appeared.  There were a couple of close calls, but I was able to eliminate the apps I thought were causing the problem by repeating the steps that I thought caused the problem.

A co-worker suggested that I look at Process Monitor from Microsoft SysInternals. I had used a file monitor product from SysInternals when it was produced by an independent company, and found it very useful, but this was the first time I’d used Process Monitor.  After running it less than a minute, the culprit became obvious: Hardware Interrupts are a part of the System Idle Process (who knew?) and it was consuming the 30-40 percent of my CPU.

But why? Is my laptop dying? No. A quick Google for “hardware interrupts high cpu dell” included a comment about an application called FastAccess that was causing a similar problem.  FastAccess provides facial recognition for login purposes; I don’t use it, nor do I use the camera integrated into the laptop’s screen, so the simple answer to my problem was to uninstall FastAccess.

It’s been several hours since then, and the issue has not reoccurred. The fan has not spun up once, and after using the laptop on battery for over an hour, it still showed at 77%. Case closed.