This is what I posted in your other thread:
The computer itself is not from Siemens.
I think you should be able to install standard Windows 7 Professional 32-bit... but you would also need the HMI software and project, as well as any add-ons, databases, utilities, etc. that the application is using.
If your computer is out of warranty, I would take a backup of the complete hard disk, and scan it using the manufacturers hard disk checking tool. If it shows problems, get a new hard disk and restore your backup to it.