Can't install 4.5.3.00 OS after 5.x. Virus TI Snow

    Hello. I'm running win7 x86, Cubase 7.5.4 and have a virus ti snow. And I have a problem:
    * Virus works at OS 5.xx but I don't want this OS because Cubase has to many crashes with this virus OS, seriosly, i saw crashes just in changing presets.
    * I've isntalled the OS 4.5.3.00 but "No virus TI can be found" Virus Control (Windows/Cubase).
    Important: I use this computer + virus since 2010 and never had troubles (before os 5.xx). Virus has 4.5.3.00 OS. Windows has the virus ti in "usb devices": Virus TI USB 2.8.45.
    So what i already did:
    *replace usb cable (3 times);
    *another usb ports (5 times);
    Help me please :)