Hello Gagan
This is a problem majorly faced by forum members who dont have updated latest software.you can download trial version from optiwave .However you evaluation period is over then you have to go for rental plan from optiwave for the time you need it.
One solution to your problem is ,you can try the trial version on another pc or laptop.But this also not permanant.if you have file from optisystem 7 then attach it and i will modify it in same version so thst you will able to open it.if you have more question then let me know .
Thank you