Desktop is bigger than my screen. How do I fix?

A Linux newbie (in the UK), I thought I would experiment with Knoppix 3.2 on this months PCplus covermount( with Knoppix v3.2 2003-05-03 EN.iso). I am booting from the cd I burned and managed to get round flickery screen problems and I have even got modem going so am writing this in Konqueror browser. What I can't figure out is the desktop size. By this I mean as I move cursor to the edges of screen the desktop scrolls a bit in all directions. If I look in control centre > Xdisplay the screen is 640x480 Is this the reason or do I need to configure desktop somehow? I was going to change screen to 1024x768 which is what I use in Windows 98se but it seems you have to restart the session to get changes to take effect but if I shutdown and reboot I am back to square one. Basically I just want the desktop to fit the screen at some resolution (preferably 1024x768). I have tried booting with various options including screen=1024x768 but it seems to make no difference. Also tried fb800x600 but boot stopped (can't remember error now). I have seen references to saving settings to a floppy and booting with that, is that the thing to do? Any help gratefully received. My machine is Athlon 1.2 ,512Mb, 40GbHD, Geoforce 2 mx200 64mb graphics card

Go here: http://developer.linuxtag.net/knoppix/bootdisks/ and
Download - boot-en.img . Go into Windows and Copy from Knoppix CD
the following files: rawrite2.exe mkfloppy.bat to C:\ .
Also put your boot-en.img in C:\.
Edit the mkfloppy.bat to boot-en.img. Launch the rawrite2.exe in
Windows, this will write an Floppy Boot Disk for Knoppix.
Put Boot Disk in FDD and Knoppix CD in CD-ROM, and set you BIOS to boot from Floppy.
Boot up and Knoppix will load, Hit F2 and enter:
knoppix lang=us desktop=kde screen=1024x768 xvrefresh=60 xserver=XFree86 xmodule=fbdev 5 dma keyboard=us

Maybe this will help, also there is another command: testcd (It Checks CD data integrity) that you can add to above line. I haven't used it.
Also, you can log out - log-in as another user (Chosse - root), to see
if this changes anything.
I'm running an Athlon XP 1600, Maxtor 40GB, GeForce 2 -MX400
(64MB), 256MB - with no troubles. I have an old monitor, an it was hard to get screen size set-up.
The screen=1024x768 xvrefresh=60 did the trick.

One other thing, try this:

Go into an Konsole in Knoppix, type su <Your Password>
and kxconfig. It brings up Advanced XFree86 Configuration to help
in setting up Monitor|Graphic Gard|etc..
GeForce 2 MX-400 is an NV11.

Thanks for the posts Cyberdude. I thought I would give those boot options a try booting straight from my cd i.e.

knoppix lang=us desktop=kde screen=1024x768 xvrefresh=60 xserver=XFree86 xmodule=fbdev 5 dma keyboard=us

and I got a 1024x768 screen no problem! Thanks for the help.

Just for information to anybody I am using an old 14" monitor. Other specs of my machine are in my first post to which I should add ECS K7S5A motherboard.

CyberDude:
When you say about logout and login again as new user does that only work if I make the floppy as you suggested and then boot from that? At moment when I logout everything terminates and eventually machine shuts down.

However the only other thing I could really do with now is knowing how to save stuff like connection settings for internet/email etc. so I can boot with these things already set up. I will have to search the forums more as I think this issue is already dealt with but if anyone can point me to a good link I would be grateful as I'm pushed for time just now.

Thanks again to The CyberDude

Managed to save settings to floppy and then restore by booting with Knoppix floppyconfig failsafe
as suggested here:

http://www.knoppix.net/forum/viewtopic.php?t=248