ST2 cannot be run on Windows 8. ST6 was the first version to support it.
You will need a new license file if your hard disk is replaced or you get a new PC. You will need to talk to your VAR or GTAC to do this. Another option might be to get current and you may want to try the Solid Edge rental program if your usage is only a month here or there.
IIRC ST2 was not supported on Windows 8. I would be surprised if ST2 will install on a Win 8 system, but you might be able to run it on a virtual machine with Win 7. Running on a VM is not recommended/supported, but might get you out of a bind.
To discuss how you might transfer your existing license to another drive, I suggest you talk to your VAR 1st.