There is no customer-service to call with such questions or when something goes wrong, but there is the Internet, and Linux support groups are very easy to find. A secondary advantage is that it runs in a far smaller footprint, and far more efficiently than Windows. That means that it can indeed breathe new life into that old system you were going to toss.
So what won’t Linux do? Well, it will not run Windows software, for one thing. Outlook, Office, Internet Explorer, certain games, etc. are all designed to run under Windows. The upside is that there are Linux-specific versions of just about any application software you need, so you’ll have ready access to a choice of web browsers, Office Automation Suites, photo editing utilities, or whatever you normally run under Windows — you just have to find them online, and then learn and get used to a new version.