A log time ago I had my peg2 in a big crt monitor and now its configured to it, I don't have acces to the monitor anymore and I need to change the screenmode to a 1024x768 but I can't see nothing because the mode its "out of range" How I can boot in a safe mode to change the screenmode to a one suitable to my small monitor? I've tryed to boot from the mos 1.4.5 boot cd but then I can't find the configuration file.
The easiest way is probably really to boot with a MorphOS boot cd.
Afterwards change to the partition that you normally use when booting from hd. Here you should look for Prefs/env-archive/sys/PublicScreen.prefs and rename this file (it contains all the defined screen modes for the defined monitor).
Now, when booting from hd MorphOS should fall back to a "sane" screenmode (640x480 or so).
Selecting/defining a new monitor and new screenmodes should be no problem afterwards.