www.wysiwygwebbuilder.com

I changed my PC, and since then when I want to view a page, a scan of all the pages begins, and instead of it taking a few seconds, it takes several minutes.

Maybe you have added custom code to the page that only works online? (for example: Google or Facebook).
It is very difficult to say anything meaningful about this without knowing exactly what you have done.

Unless you've got the option "Preview Scope" set to "Entire Website"?
It's in Options > Publish > Preview.
BTW, the option can be toggled by using Shift-Preview.