Where is startx ?
 

I installed a clean install of Arch yesterday

Installed KDE but did not make it start automatically

Now i enter 'startx' to get to KDE and it says there is no such command !!

If i run the init script for kdm then kdm starts ok and I can login from there to KDE

Where is startx ?

Please check default runlevel in /etc/inittab.
Change default runlevel to full multiuser and X11.
Something like :-
# Default runlevel. The runlevels used are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
#
id:5:initdefault:

The startx script is ..
"".. just a sample implementation of a slightly less primitive interface than xinit""

'xinit' can be used. May be an original Arch has no /usr/bin/startx ?

The /usr/bin/startx from Arch alias Chakra is attached ( 4.4 kB )
..

Startx comes with the package xorg-xinit. The executable is located at /usr/bin/startx. Configure it in ~/.xinitrc