the moral of the story here... is upgrade to WindowsXP
aside from that what you can try is this.
If your in safe mode you'll know about it because in each Windows except 95 you get the words "safe mode" in all 4 corners of the screen. (as if the UI wasn't already cramped enough eh)
now the first option you can try is this, when your system displays "now loading Windows98..." or something to that effect press F8 or F5 one of them will work and you'll get an options screen.
This time your going to deliberatly choose Safe Mode (w/o networking) ... let it boot up and everything will look horrible, don't worry this won't be the case after we tinker with a few things.
Now first order of business is to find out if any drivers are broken or not loading (as this sounds like to me).
So right-click on My Computer and choose properties from the menu.
You'll have a little screen appear with you major computer details, click to tab called "Device Manager"
Now check down that list to see if you have any yellow (triangle) attention or red (circle) warning symbols.
if you have we've atleast identified the problem here, if not then gimme a little while to think about a next step cause 98 doesn't have system restore.
But i think it'll be a safe bet your graphics cards drivers were broken and will have a warning symbol next to them ... (will be the symbol with the little monitor called Display Adapters)
Double click on your cards name, should be under that icon - if not you've really done a number on the system lol
And it should either goto a tab menu saying "driver broken using default PCI adapter" (or something to that effect) else it'll bring up the Add Hardware Wizard.
Now you'll need you driver CD/Disk ready, if you don't have one then you'll have to manually pick what your card is (which can be a pain as i dunno what it is so i can't instruct you on that, and it isn't a guarentee the Bios at bootup will tell you as some cards do a bios boot and some don't)
I'm gonna hope you have the CD anyways ... first thing to try if to put the CD/Disk into the drive and run "Automatic Update/Search"
if it fails to find anything then press back, go manual/advanced selection ... scroll down to display adapters, and underneath the second window is a button saying "have disk" then you can manually select where the driver is on the CD/Disk.
(if you don't have a disk and were using windows drivers, get your 98 cd handy and go down the left hand list to find your cards manufacture/chip maker then the right hand list for your chip type then click NEXT)
After that is done you can then close the Device Manager just clicking OK to everything and when it asks if you want to reboot, say NO.
RightClick on a free peice of screen and click properties. This'll bring up your display properties, goto the setting tab and set the resolution and colour depth you want.
Now reboot when prompted.
It should fixx the display problem, however the other problems might be the cause of something else.
you may wish to get a virus checker from somewhere, like Norton Anti-Virus or McAfee use thier online checker to check your system over ... as you maybe infected with something for this to happen.