where does MySQL store database files?

WAMP stores the db data under WAMP\bin\mysql\mysql(version)\data. Where the WAMP folder itself is depends on where you installed it to (on xp, I believe it is directly in the main drive, for example c:\WAMP\...

If you deleted that folder, or if the uninstall deleted that folder, if you did not do a DB backup before the uninstall, you may be out of luck.

If you did do a backup though phpmyadmin, then login, and click the import tab, and browse to the backup file.

Check your my.cnf file in your MySQL program directory, look for

[mysqld]
datadir=

The datadir is the location where your MySQL database is stored.

For WampServer, click on its tray icon and then in the popup cascading menu select

MySQL | MySQL settings | datadir