The laptop I use is Dell XPS M140. I just upgraded it from 1 GB Ram to 2 GB ram.

Answer:
I agree with the first answerer, it is a power saving feature. The processor speed (clock rate) will fluctuate. When you aren't doing anything that requires a lot of CPU power it will lower to save battery life but when you need the CPU power (eg. playing a game) it will go back up.

Windows XP Tip:

Sometimes you can make the laptop stay at the faster speed. This is useful if you’ve it plugged in to a wall outlet and aren't concerned with saving power. This may work on other operating systems too but I only know the instructions for XP…

1. Open the Power Options (either from the icon near the clock or from the control panel)

2. In the “Power schemes” box select “Always On”

3. Click OK

Now the processor should stay at 1.86GHz all the time. This may or may not work depending on your laptop but it works on mine.

Answer:
This is probably a power saving feature, by lowering the CPU speed it uses less power, and it will go back up to 1.86ghz when you’re doing something.
Answer:
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