There are many solutions.
You could create a new SSID for the desktops (and attach the desktops to that specific SSID) and then limit the bandwidth of the other SSID.
You you use tags, and put the "general" SSID on all AP's except the one in question, and put the "desktop" SSID on the AP in question.
Assuming that an AP is near the desktops; you could increase the minimum allowed connection speed on the APs. This would encourage other users to more aggresively roam to a closer AP and away from the AP near the desktops.
You could attach a schedule to the "general" SSID turning it off at a specific time of the day and leave the "desktop" SSID on.