backing up drupal/joomla work, need to reinxtall xampp

[kggmvmv]

I've been using XAMPP on my WinXP+SP2 box for about 2 weeks,
and been playing with Drupal for the last week or so.
(That was the point of this exercise.)
What with one thing and another, I've gotten my server very confused,
to the point that (after starting Apache, MySql, and Mercury, of course)
when I enter http://myhostname, I get the purple-and-yellow page
saying "Welcome to Localhost", and if I enter, http://myhostname/drupal
(which only a few days ago worked), I get a blank page.

Oh. Oops. That's with Mercury not started. If I start Mercury,
then I get "Access forbidden" (error 403).

Well, I know I was experimenting, so I'd just like to uninstall XAMPP,
and re-install. However, I *would* like to save the Drupal work I had
done (just some demos, but interesting),
which supposedly just means backing up the MySQL database.

However, I cannot find the MySQL database data files.
Worse, I cannot find the mysql command,
to be invoked from the C: prompt or from CygWin.

Can someone point me in the (or a useful) direction?