(Tested with XAMPP 1.7.1)

Install XAMPP, set Apache as a service and start it.

Edit C:\xampp\php\php.ini:
Change safe_mode to On
Remove the semicolon in front of this: extension=php_pdo_sqlite.dll

Run the security wizard:
http://localhost/security/index.php

Make sure you have a firewall!! Otherwise you will open up your finances to the world.

Open the XAMPP control panel and restart Apache.

Create a folder: C:\xampp\htdocs\clearbudget

Extract clearBudget to this new folder.

Browse to http://localhost/clearbudget and enjoy!

If you decide you want to open up your firewall for others to access your checkbook (accountants, etc.), I *highly* recommend you purchase an SSL cert. Self-signed certificates ARE NOT SECURE as they allow man-in-the-middle attacks. If self-signed certs were secure then all companies would use them. Fortunately there are companies like Comodo or InstantSSL who offer certs for much less than Verisign/Thawte, and they're every bit as trusted.

Note: XAMPP's SSL is not enabled by default. If you use it, disable regular http port 80 on Apache so you don't accidentally expose your password. Also, reviewing an Apache security document is a great idea. I'm not 100% sure the default install is secure.

And keep your XAMPP up-to-date. I'm a bad example, running two versions behind :-)