A. The service pack installation process estimates the amount of disk space required to apply the updated files and adds 30MB for safety. If the amount of free space on the partition doesn't meet this minimum requirement, the installation will fail. Systems administrators often configure a very small System partition (the partition that contains the ntldr and ntdetec.com files). If this partition has less than 30MB free after the installer determines the amount of space required, the service pack installation will fail, even though the installation requires only about 300KB.
To work around this limitation, you can manually update the files (i.e., ntldr and ntdetect.com) on the System partition that the service pack updates by extracting the service pack (type "w2kspx.exe -x" without the quotes) and manually copy the files onto the System partition. When the service pack installation process runs and sees that the System partition is up-to-date, it won't require any additional free space on that partition and will let the installation continue.