Get yourself a 6.4GB hard drive, leave the current Windows hard drive where it is, disconnect the power connector and IDE ribbon cable from the Windows hard drive, connect up the clean 6.4GB hard drive, and install VectorLinux on it, just as if the Windows drive doesnt exist. When youre through playing with VectorLinux, disconnect it, then reconnect the Windows hard drive, and the computer will never know you made the switch.
Just be sure to shut down and disconnect the computer's power cord every time you switch the connections on any drive. After you shut down and disconnect the computer's power cord, wait 30 seconds before you make any changes. (The motherboard has residual power for a little while after everything is turned off.)
Re: size of hard drive for VectorLinux 5.8 Std
You need at least 4.3GB, 5.0GB is better, 6.4GB is ample, 8.4GB is plenty, 10.2GB is more than enough. (3.2GB is bare minimum)