Record button does not work

Every time I press the record button my pc reboots.
I’m using the latest version of AudaCity, 2.0.5.
I have recently re-installed my pc with Windows XP Home.
I have obtained the .exe installer.

Several weeks ago I could still record while playing my guitar but after I had to re-install my pc I’ve got this problem.
I don’t know what I have to do to resolve this problem.

I would strongly suspect the problem lies with the sound card drivers.
See here for how you may be able to fix it:

Your solution was absolutely right.
I have updated my sound drivers and AudaCity works like it did before.
I am very pleased with your answer and specially for the quick respons.
You make me a very happy man.