Here's how I've done that in the past.
First, I add a hidden text field to my list called LastSetupWorkstation
Then, in workflow that runs on an item changing, check to see if all the boxes are checked - you have to use 'contains'.
If they're all checked, see if the last field is missing any of those - that means the current change has a new checkbox.
Once you're done, set the hidden field to the value of the actual field, so you don't do an email when another field changes.
If CurrentItem:SetupWorkstation not equals CurrentItem:LastSetupWorkstation
If CurrentItem:SetupWorkstation contains Desk Location
and CurrentItem:SetupWorkstation contains Computer
and CurrentItem:SetupWorkstation contains Email Accounts
If CurrentItem:LastSetupWorkStation does not contain Desk Location
or CurrentItem:LastSetupWorkstation does not contain Computer
or CurrentItem:LastSetupWorkstation does not contain Email Accounts
then Set LastSetupWorkstation to CurrentItem:SetupWorkstation