I have done this, and it is very helpful. Give it a try before you dismiss it!

You seriously won't believe what you'll find. For example, new laptops purchased from a big box have so much crap starting up that they make the laptop run poorly. It might seem obvious to you what programs should be uninstalled and easy for you to do it, but that's not true for other people.

Just email them and say you'd like to setup a chair in their office X day(s), all day, and anyone with any computer problems should come see you and you'll do your best to help, no job too small. I think you'll find your offer well received and useful, but there's certainly no harm in testing it out.

As a computer person, you're in a unique position to help and you can have a big impact. Don't dismiss this idea so easily!