I use Caffiene for my Mac.The link goes to a PC version. It is great when downloading files and such. Just click on the coffee cup in the toolbar and it wont sleep till you click again.
Oh it is free too.

Be careful. I work in IT- they set these up for a reason. I would try appealing to the IT department letting them know you dont deal with any secure data.

However, I bet I could argue almost any job function has secure data.

Good IT departments can tell when you install something that shouldnt be there, that interferes with what we set out to do. At my company, you get one warning, then you get fired if you do it again.

Just be careful.

A batch file which periodically changes the focus of the current window would do it. If you aren’t computer savvy though, I certainly would follow @mowens advice.

Also, remember that you are responsible for any emails that are sent out from your account. If your computer is locked out, and someone who is upset with you walks by, could send an email to whomever you want. Ive worked for large companies, and some smaller ones. All agree. The second I turn my back on my computer, I press the windows key, and tap the letter L. This locks my computer. I type my password probably a couple hundred times a day, and I wouldnt have it any other way.

This is how conversations have gone, when I have sat in with HR and employees who have had their account do something nafarious.

HR:
Why did you do (insert bad thing here)

User:
I didnt. Someone else did it from my computer.

HR:
You gave someone your password?

User:
No, they sat down at my desk when I wasnt there.

HR:
You are responsible for any actions that are done from your account.
(user gets written up)

I have seen people get fired from the first offense, depending on how bad it was.

@mowens A home computer is a little different, especially if you trust the other person in your house. You cannot do stuff from my computer without me asking what the fuck you are doing in my house.

But for a work computer, it’s best to leave security measures in place; they are there for a reason.

Place a cheap watch, with the face side up, under your mouse when you walk away.

@jerv I agree, sorry I didnt see he said it was his home computer. My bad. :)

@mowens It was a little ambiguous. Best to cover both bases, especially since other people with different situations may be reading.