All Sennheiser PC and Gaming headsets are designed as plug and play devices so you don't actually need any software to have functionality of the headset on a computer. The Sennheiser HeadSetUp software that you can use with the headset simply provides an easier interface between the PC and headset. If you want to use the Sennheiser HeadSetUp software you can get it here: (http://en-us.sennheiser.com/cco-software-download-for-pc).
To connect a PC or Gaming headset to a computer the cable needs to be connected to the computer's USB or dual 3.5 mm jacks or single 3.5 mm dual way audio jack depending on the connection that is available. NOTE: Depending on the connection on the headset cable and the connection on the computer an adapter may need to be utilized to make the connection.
Once this connection is achieved go into the computer settings and select the headset as the default playback and default communication device which will put all sound from the computer through the headset. Typically to configure the settings of the computer adjustments are done through the control panel and then through audio devices or sound & audio settings. NOTE: When using soft phone software adjustments to the soft phone settings may also be required.
If the headset is only to be used for communication applications and other computer sounds (like alert tones) need to come through the computer speakers then the configuration is slightly different. The computer speakers need to be selected as the playback device and the headset needs to be selected as the communications device. NOTE: This level of functionality will be determined by the configuration of the computer software/settings.