First of all if you have any information that you want to save - back it up - to a CD , USB Stick, external HD or where ever you want to save it.
If you have the Windows Vista install disk, you may want to reinstall and let Vista install using the entire disk. Then defrag it at least twice.
Now download the EASEUS
partition manager ( here is the link to the download ) = http://www.partition-tool.com/personal.htm
and use it to shrink the installed Vista partition. ( The EASEUS software is very easy to use and is Free to download and use )
Next, put in the PCLinux Live CD- let it boot up - click on the install icon and follow the install prompts, let it format and install in the free space that was created by shrinking Vista - at the end of the install it will install and set up the Grub boot loader - which will then allow you to boot PCLinux or Vista.
Hope this helps ! - and I am sure that some of the other forum members will come along shortly and suggest other options - as I am not the sharpest pencil in the box !