You don't need to download anything.
Do this:
Go to your steam directory. Then steamApps, call of duty black ops, players
Open "config" with Notepad
Copy the bold text and paste it on the bottom of the text.
Save.
Right click on "config" -> Properties -> Read only
seta thereisacow "1337"
sv_cheats "1"
bind o "sf_use_ignoreammo 1"
bind i "g_speed 400"
Here you go. Go in-game. Press O for unlimited ammo and I for speed hack.