We have few licenses of ST2 and few ST7
In order to view ST7 files we tried to install ST7 viewer on ST2 computer. But it's not getting installed. .
Is these a conflict between ST2 and ST7 Viewer being installed on same machine?
You will need to uninstall the ST2 viewer first, then install the ST7 viewer. Both viewers cannot exist on the same machine. However, the ST7 viewer can view ST2 files so you do not need both installed.
Also, is the Windows platform a supported ST7 platform? XP is no longer supported with ST7.
Okay, let's word this differently -- the ST2 product and the ST7 product, regardless of which products they are cannot exist on the same machine.
So to specifically answer your question, no you cannot have Solid Edge ST2 installed on the workstation and then attempt to install the ST7 Viewer.
Regardless, you could run a multiple Solid Edge install by using SESetActiveVersion.exe but this is not a supported method for production systems. See the Solid Edge readme file for more on this functionality.
You could also create a virtual system with just the ST7 viewer installed on it.