See this from Microsoft
I have a Dell Computer running Windows XP Professional. The total size of my hard drive is 55.8GB. The C:\Windows\Installer folder takes up 47.7GB of space. Inside the Installer folder are files with the extensions msp & mst. These files add up to 5,327. Windows tells me that I am low on disk space. Could I possibly delete some files in the Installer folder to regain some space without anything bad happening? The computer only has two major programs on it. They are Office 2007 & Norton 360. Any help would be greatly appreciated. Thank You!