Safari is a good browser, but no browser is perfect, and everyone (even Windows users) needs an alternate browser, if for no other reason than to check a strangely-behaving page to find out if it's a browser problem. All the browsers listed here are free downloads.
Probably the best alternate browser for both Mac and Windows is Firefox. Currently in version 2, Firefox is easy to install, easy to use, works well with almost all web pages, and is supported by the Help Desk.
Download: http://www.mozilla.com/
Opera comes fron Norway, but like most things Norwegian, its English is impeccable. Now in version 9, Opera is also available for Mac and Windows, and is easy to install, easy to use, and works well with almost all web pages. Unfortunately, it is not supported by the Help Desk, but it's still a good choice as an alternate. One of its unique features is its ability to disguise itself as another browser on a page-by-page basis.
Download: http://www.opera.com/