I often hit caps lock by accident. My brain can type 350 words per minute, but my fingers struggle to reach 80wpm, so they get a little confused sometimes !
If you are reading from a document and typing, or if you dont touch type,so you need to look at the keyboard when you type - if you have accidentally locked your caps on you wont know, until you look up at the monitor and see 3 sentences which are in caps.. ooooops...

There is a solution to this. Its called 'toggle keys'. Enabling 'toggle keys' will make windows sound a tone when you hit the numlock, scroll lock or caps lock keys. The tone is different for on and off. If you are typing madly away, and hit one of these keys, you'll hear the tone and stop before you type a whole paragraph in caps! It wont even matter if you have no sound.. the sound will come from the computer, not the speakers!
To enable 'toggle keys' in XP, open your control panel. Using the 'classic' view, select 'accessibility options'. Under the 'keyboard' tab, you'll see a check box for 'toggle keys' Tick this, save and your problem is solved!
To enable 'toggle keys' in Vista, open your control panel. Click on the 'Ease of access center' icon. Click on the 'make the keyboard easier to use' link. Now tick the 'Turn on toggle keys' box and save.
NOTE: In Vista, there is an extra option. If you also tick the link which says 'Turn on toggle keys by pressing the NUM LOCK key for 5 seconds' then you will be able to enable or disable 'toggle keys' by doing just that, without returning to the control panel. I personally wouldnt use this, even if I had Vista, as once its switched on, I leave it on. I am sure you will too, as this is an excellent feature.