I used both XAMPP and WAMP in Windows and found their general performance and reliability to be pretty poor. I guess when you install them they aren't exactly as optimised as they could be.
So, I use Zend Server Free Edition now.
It includes lots of bloat, actually, but I tend to just install the Server part and the bits relating to performance and caching (Zend Optimizer etc.) and it works great.
It always wants to install your htdocs folder in C:\Program Files\Zend\Apache2\htdocs though so in later version of Windows you'll get User Account Control problems so you will either need to move htdocs to another location that is writable (my documents, etc.) or make your htdocs folder specifically writable and override any inheriting permissions.