NCDYNC is a service tool which will be able to update your NameCheap DNS with your host IP. And it is also an open-source software you can free to download the source file (ncdync.cpp) and modify it to do whatever you want. I have compiled it by using mingw gcc 4.5.0 so you do not need to compile it by yourself.
How to use?
First of all, you need to download it from my website http://intgrow.com/ncdync/ncdync.exe, and open command-prompt window. Please note, open it as administrator if your operating system is Windows Vista/7 and UAC is enabled.
1. Enter command ncdync.exe /install to install the service to your system
2. Enter command ncdync.exe /defaultconf to make a default config.ini on current directory
3. Edit config.ini and modify your domain name, host name and password, you can enter multi-lines to indicate the program updates multi-domains.
4. Start the service from control-panel
5. Use ncdync.exe /uninstall to remove it from services manager
How to setup namecheap domain records?
Check it out – http://namecheap.simplekb.com/kb.show?show=article&articleid=43&categoryid=11
Visual C++ 2010 express version
I have also compiled it by using Visual C++ 2010, you can download it here, the VC version is able to set the intervals of update in seconds. use /defaultconf to make a default config.ini and you will know how to modify it.
Send it via email firstname.lastname@example.org