The last release of FrontPage was in 2003, I think. So it's 10 years behind the curve, in an industry that changes all the time. So unless you have some personal attachment to it, I would migrate away from it. The only stickler I know of are the proprietary "FrontPage Extensions", which are run-time server components that could optionally be used in a FrontPage web site. If those are used, you would need to ensure they either stay on the server, or that you convert them to another server language. You could ask the server administrator if those extensions are on the server - hopefully they are not being used for the site.
Presuming you do not need FPX, you can edit the site with any editor of your choosing.