Hi Hadassah143,
What is the operating system of your new computer? Windows 10 and OS X 10.11 have both been known to create problems with older software like CS5. OS X 10.11 El Capitan, in particular can prompt misleading error messages due to its default security settings. To bypass this, go to security in the Apple menu, and, under the Security and Privacy General tab, change the toggle to "Anywhere". When you are finished installing, reset Gatekeeper to your preferred security setting.

If this does not address your issue, can you provide more detail to help us troubleshoot? Are you downloading from Download Adobe Creative Suite 5 products? If so, are you getting a specific error message?
Best,
Del