FDV here. Too lazy to log in again...
1. Are you installing from a boot floppy, real mode CD-ROM drivers, and a CD, or installing from a bootable CD right from the CD w/o use of a floppy? (Why? I\'m not sure, but sometimes, using a boot floppy causes copyfile errors on slipstreamed installations.)
2. Are you SURE that when you expanded the Service Pack 3 file, _all_ of the files are there and none were deleted? This is classic behavior of a slipstream that is not finding all of it\'s files.
Now. On to theoretical discussions of a fix for you.
Some notes on slipstreaming here:
http://home.earthlink.net/~vorck/Though this is geared to removing IE, you\'ll discover that this process lets you know what kind of things you can do about screwing around with slipstreaming safely, which you can ultimately do if nothing else works. (Mod the copyfiles sections to omit the files you get the error from, then put the files you need in an $OEM$ configuration to copy later).
Hope this works for ya,
Fred