if its from speakers, I'd say it's an audio loop, the little click you heard was the click of you clicking the button, generated by windows....god knows why they built it in but hey. What happens when it hangs is it often executes the commands it still has bufferd over and over and over...which is why you heard the click over and over....you may have run into something like it with games, where if it crashes...the sound gets stuck......can drive you nuts.
How ever if it's from the PC speaker (The one on the inside) it is probablyyour system beeping at you because it is too busy to take your input at the time...again..another Windows feature.
I may be wrong, but thats my guess.

- Noia