How can I open a rar or flac file that I downloaded?
There are many programs out there - some free, some commercial - which can open RAR archives. As for FLAC files, FLAC stands for "Free Lossless Audio Codec" - and plenty of good media playing software should be able to handle FLAC files. Winamp, for example, comes with FLAC support, although you may have to tick a box for it when installing.
A great resource for finding out what different file extensions mean, along with what programs they are for, is filext.com - just type in the file extension and hit the button, and it'll give you a whole bunch of information about it.
You've posted a comment on my profile saying that you're having problems installing WinRAR. In future, you should either post such additions to questions on the original thread, or if you really want to ask an individual person, use Fun Mail - either from the "Fun Mail" link at the top right of the page, or the "Send me Fun Mail" link under their username at the top of a message they've posted.
If you are having problems installing WinRAR, though, you might like to try an alternative such as 7-zip, which is totally free (rather than being a free trial like WinRAR).
My favorite is the open source software "IZarc"
it recognizes most types of archive files, and is free (or used to be).
Rars can be opened with Winrar, a free archiving application like Winzip. You cna download it at rarsoft.com.