Segoe UI is alright, it's better than the Windows 7 font, it's just a guess was it Calibri?
Segoe UI is the default UI font starting from Windows Vista and Windows Phone 7 (as Segoe WP, a variant). It's tweaked in Windows 8 to look slightly different (it's closer to WP). It's definitely the default UI font in Windows 7. (Not all desktop applications respect that. Some might use Tahoma, Microsoft Sans Serif, or - worse - the bitmap version of the latter!)
Some applications on Windows XP that came from later in its life also use Segoe UI. The Zune Software uses Zegoe UI - yet another variant. They're pretty similar, but do have subtle differences between each other.
Calibri is the default font for Microsoft Office 2007 and Office Mobile 2010 onwards, as well as Windows 7's WordPad.
It's not just Segoe UI that's in the "new fonts for the new operating system" game. Meiryo UI = Japanese equivalent, for an example. There are also a lot of "Segoe UI"s for other languages, which all come preinstalled in a new computer these days. Segoe UI itself also has a variant for symbols, fittingly called "Segoe UI Symbol" that has tons of symbols (as well as the basic set). (IRC users: this is to your great advantage.)
Speaking of the Segoe family...
Segoe Keycaps: Used for displaying letters as if they were actual keys. An "A" would look like an "A" with a rounded rectangle surrounding it, mimicking a keyboard cap.
Segoe Marker: Has a "written with a marker" feel. Also usable for mathematical use.
Segoe Script: Written like a script.
Segoe Print: Less sloppy version of above - each letter is a print letter (non-cursive).
Segoe UI: UI font.
Segoe UI Mono: Fixed-width variant of above.
Segoe UI Symbol: Used for Unicode symbols that is beyond Segoe UI.
Segoe WP: Variant used in Windows Phones.
Most of these fonts have multiple weights in addition to regular and bold. Some variant of "light" almost always exists.