For the meaning of bootup look here -
What is boot? - a definition from Whatis.com - see also: boot up, booting
During the bootup process, Press F8 key.
If you see a boot up selection displayed, press ESC key, then continue to press F8.
This will bring you to a page that will offer many options.
Select Safe Mode
Once in the Safe Mode, shutdown your computer.
Once shutdown, bootup again (do NOT press F8 this time).
If your computer will not allow you to do the above, place your Windows Installation CD in the CD drive and bootup off of the CD drive. When you get to the page that offers the option to Repair for problems booting into Windows, press the R Key. Do NOT select "Install".
Good Luck...