problem with a reserve monitor

Having to replace my monitor temporarely because of a repair, I connected a reserve monitor to my system. I am running SuSe 8.0 on a pentium II with s S virge video card. Before removing my 17" monitor which I run as Vesa 1024x768, 16 bit65536 colors and a refreshrate of 60Hz I changed the values to 800x600. I do nothave any information on my reserve 15" monitor. After closing down my system I made the change of monitors to be surprised with unreadable row of screens . I knew when to give my username and password and after the input of startx (I always start in console) I was surprised with a readable and usable GUI. How can I get the the boot process readable again with this monitor? Somebody a solution?