OK - I will make this into a sticky in a bit
Note there is NO Upgrade for 1.8.0 - reason - things (features, settings, configurations) are too different when you hit a major release on Apache or PHP. XAMPP 1.8.0 has Apache 2.4.2, prior XAMPP releases were 2.2 - big changes. CHECK with any third party scripts to make sure they are compatible with Apache 2.4.2. Ditto check any changes you made to any of the Apache .conf files, some common features are deprecated - most notably this would be the 'NameVirtualHost' directive and 'most' versions of simple authentication methods (mod_auth... Apache Module versions), including the .htaccess syntaxGoing from XAMPP 1.7.7 (or other versions) to 1.8.0 for WindowsA. BackupBackup your 'custom' / user added MySQL databases. You can use the phpMyAdmin export tool, MySQL Workbench (free tool from Oracle), or the mysqldump.exe Command Line tool. Take screenshots of your database names, users and settings. Make SURE you know all the passwords and they are working (you can test by logging into phpMyAdmin as those users). You will probably have to 'add-back' any users 'you' created originally (like for the WordPress 'database user') and re-create the empty databases and the user privileges, don't forget the PMA control user This is the safest route unless you know 'a lot' about MySQL Imprt/Export parameters. Copy out your HTDOCS, any user added Folders that are Aliased, and any Virtual Host folders.
B. Stop XAMPPStop all XAMPP processes/services.
C. Complete BackupBackup your complete XAMPP install to another location. This could be by way of a true backup program like Acronis or Fbackup or simply shutting down XAMPP and copying the entire folder to a new location.
D. Save ConfigurationsIf you have modified the Configuration files for Apache, MySQL, PHP, and PHPmyAdmin (config.inc.php) they will likely need adjustments. (You will have to figure that out) I save them AND the log files to a XAMMP-Move folder for myself. If you are going from an earlier version, this is 'doubly true'.
E. Un-install ServicesIf you made Apache, MySQL, FileZilla, Mercury or Tomcat into services, un-install/remove them from the Windows service manager via the Control Panel, or by way of the Command Window using the Windows 'sc delete' command.
F. Clean UPOK, you should be ready for this - DELETE the current XAMPP folder.
G. InstallNow either:
Use the XAMPP Installer
or
Expand the .7z or .zip downloads. Copy the new 'xampp' folder to the location of your old installation.
H. Start the New XAMPP InstallStart up the Control Panel and debug the new installation before you bring anything back.
I. Check UpCHECK (again) with any third party scripts to make sure they are compatible with Apache 2.4.2. Ditto check any changes you made to any of the Apache .conf files, some common features are deprecated - most notably this would be the 'NameVirtualHost' directive and 'most' versions simple authentication methods, including the .htaccess syntax. Make needed changes to the Apache .conf files php.ini and my.ini to get your install 'like the old one' or as close as you can come.
J. RE-installOnce everything is stable, REINSTALL any third party scripts and follow their instructions to 'restore' as if it were a 'server' move, because that is what you have just done.
Good Luck