A. The calculation below can be used for disks of a standard 512 bytes per sector:

  • Take the size of the partition and divide by 100. If this is less than 1,048,576 use 1,048,576, if greater than 4,194,304 use 4,194,304
  • Add to the number calculated above the size of the partition divided by 803
  • Add to the number calculated the total number of files and directories multiplied by 1280. You can work out the total number of files and directories using the dir /s command at the base of the partition, e.g.
    dir /s d:\
    Total Files Listed:
    3397 File(s)
    300,860,372 bytes
  • Add to the above 196096

To summarize:

Free space needed = (<size of partition in bytes>/100) + (<size of partition in bytes>/803) + (<no of files & directories> * 1280) + 196096

For more information see Knowledge Base article Q156560 at http://support.microsoft.com/support/kb/articles/q156/5/60.asp