One thing you need to be aware of is that it might have run out of disk space -- did you see any errors when unpacking it?

Can you do the following steps and post the output?

df /
echo $PATH
ls -ld /usr/bin
ls -l /usr/bin

The first tells us whether you ran out of disk space on the root partition. The second tells us where it'll be looking for executables. The third tells us about your /usr/bin directory itself. The fourth tells us about what's in your /usr/bin directory.