'Slow' is a relative question, so first determine what the user is experiencing. Is it slow opening applications or while working in them? is this a networked application or local? If it is a website or network application, the tech can try to open it from their workstation. When did this start? Can you check co-workers sitting near you to see if they also report slowness?

Also, ask the user what, if anything, has changed since it was working 'correctly'. Ask if the user is working from the location they normally do -- maybe they are working at an alternate workstation, working from home over VPN or other issue which they might not realize is a factor, so they fail to inform you.