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You may find that at some point your C: drive begins to get full. Sometimes this can be due to your Windows directory getting bloated. There is something that can be done.
However this does require the existence of another partition or hard drive on your PC.

Please note that this will only work with versions of Windows up to XP and Server 2003 and remember any changes you make to your system are at your own risk

%windir%\servicepackfiles is where the directory is located

Follow the instructions below to change your "servicpackfiles" location

Create a directory on another drive, I tend to make another windows directory and move the servicepackfiles (including subfolders) directory there
Run regedit and navigate to the following key;
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup

There are possibly two keys which require their values changed
ServicePackCachePath
ServicePackSourcePath

SourcePath will read something like c:\winnt\ServicePackFiles
CachePath will read something like c:\winnt\ServicePackFiles\ServicePackCache
(dependant on OS, this might be windows not winnt)

Change these values to reflect where the directory has been moved to.

Sometimes the I386 directory can be within %windir% and this runs to several hundred megabytes.
Look in the same registry section and if there is SourcePath and it pointing to %windir% then this means that within the windows directory there is an I386 directory.
If you have a D: drive/partition then move the I386 directory to the root of that drive and change the SourcePath entry to d:\

Instant savings.