The Universal Print Driver (UPD) is designed to be a single driver that gives users instant access to a range of HP print devices--in the office or on the road--without downloading separate drivers.
However, it is a print driver only. It does not include a scan driver.
According the UPD specifications tab, the Officejet 7310 is not on the supported product list. However the Laserjet 3050 is. This would explain why you could not get the UPD to recongize the Officejet 7310.
For future reference, the UPD site offers a supported product list under the specifications tab (scroll down). This list changes as new devices are added to on a regular bases.