Typing sound in laptop

I was reading the online news this morning when I got a popup that said, "Windows Update Store Manager has stopped working" (or something simular) and when I closed the window, I heard a typing sound. I have heard this sound (like someone is typing on my laptop when no one is) before, but I couldn't connect it to anything. Any ideas:
HP G60 Notebook PC
ST9320320AS ATA Device
Slimtype DVD A DS8A2L-A Device
Pentium (R) Dual-Core CPU T4200 @ 2.0 GHz
Memory (RAM) 3.0 GB
32-bit OS
Windows Vista Home Premium Service Pack 1

And I heard it again when I opened the System box to get those specs.