Hi,
Install Knoppix using the CD on the HD. (You did this already)
(Eventually reboot using the bootfloppy)

Press Ctrl/Alt/F1, you are in the big black commandline screen.
(To get back later to colored display: press Ctrl/Alt/6or7or8..)

Login as root including password.

Then type dd if=/dev/hda3 of=/bootsect.lnx bs=512 count =1
(hda3: the '3' points to the linux partition, could be 2,3 or 4 or 6 depending
on the other Dos/Windows partitions installed)

Put a blank formatted diskette in the drive.
type in: mcopy /bootsect.lnx a:

Now you have a valid bootsector for Linux on the floppy!

Now get out Linux, back to Windows.

Copy the file bootsect.lnx from a: to c:

Add the next line to boot.ini:
C:\Bootsect.lnx="Linux"
Save, reboot, select Linux when selecting the OS and there you go!

Remember: if you ever change lilo.conf, don't forget to run lilo AND
repeat the above procedure!!!!! Otherwise you wil get a screenful of 99's!

Btw the procedure described above is not my invention: it is based on a nice article written by Bruce P. Blackshaw named:
"Dual booting Linux and Windows 2000 on large hard disks"

(This trick works with XP and W2Kl! BUT..... you will have a problem getting your networkcard working: some Windows security updates kill some settings in it.....so that only Windows works fine, not Linux....)
See interesting stories at
http://www.knoppix.net/forum/viewtopic.php?t=2164

Good luck!

Niels