Did you install XAMPP 1.7.7 into the C:\ drive so you have C:\xampp as the installation folder?
Can you use the new version 3 Control Panel found in the XAMPP folder:
as it has a better log window that gives more detail.
First Exit the older version 2.5 after Stopping any XAMPP components you may have running.
Also this new version has a Netstat button that may tell if there is anything using port 80.
For the latest version the download is linked to in my signature 'Control Panel Version 3' button tab.
Simply extract all the files and folders from the CPv3 folder found in the archive to the xampp installation folder and overwrite when asked.
Then right click the exe to create a shortcut to the desktop, for example, for easier access.
This version 3 (XCPv3) control panel has many new features including a much more detailed log window to help with troubleshooting start issues.
Also please read the \xampp\apache\logs\error.log file for clues why Apache can't start.
If you don't see any log files in that log folder then you may need to read on.
XAMPP for Windows 1.7.7 is compiled using VC9 (Visual C++ SP1) and so the runtime file (Microsoft Visual C++ 2008 SP1 Redistributable Package (x86)) is needed and can be downloaded then installed using this Microsoft link which also contains full information:http://www.microsoft.com/download/en/de ... px?id=5582