It has been a while since I posted, but here is a very quick tip, not 100% SQL related but it certainly applies to SQL Server installations after SQL2005.

You might notice that in the C:\Windows\Installer directory you have got lots and lots of files, over time you can end up with potentially giga bytes in there. This directory is used as a cache for MSI or MSP files used for installations of software that use Windows Installer. Now for SQL you get a new file for each instance installed, so you may well end up with multiple copies of the same file, fortunatly when files are copied into this directory they are assibned a random file name. Also when you start applying hotfixes and service packs they also ent cached, so you can probably see that this directory is going to grow quite large.

DO NOT delete the files from this directory, if you do, you probably won't notice anything until you have a hotfix or service pack to apply to SQL its going to fail if it can't locate the cached files from previous patches or the original media.