Try this.
Before you make a graphics folder or kits/players you need to unrar the file you have downloaded first.
I used RaZilla. A free download.
FreeRaZilla
Once you have downloaded RarZilla just open it and then drag you facepack or kits file on it.
In 2 seconds it has been unrar'd
Now go to documents
Sports Interactive
Football Manager 08
In here make a new folder and name in 'graphics'
All your graphics can go in here, I found it easier to make sub folders within graphics for each download
Players
Kits
Logos etc.
Now move your recently unrar'd folders into here.
Now open your game.
Click options
Prefernces
Display and Sound
Un tick USE SKIN CACHE and
tick ALWAYS RELOAD SKIN ON CONFRIM.
Now tick confirm...
this should work.... It worked for me...
Hope this helps.
Mia