There is a slider but no numbers on it, just a slider and a pointer telling you that if you slide to the right the game gets harder.
The first time you look at the list of game play options just after starting the game you click on gameplay and a new screen comes up with a number of auto save game options and at the top of the list is the slider. The slide is set dead center. I would assume as the normal Default setting and that gives you the option to move to the right for Harder or move to the left to make the game easier.
I left the slider in the middle (Default) because I really didn't think about it when I started. Maybe next game I'll try a higher setting but for now default works for me.
As far as the rest of the game I think you shouldn't have any problem playing.
most of the game is point at someone close and hit space bar or hit the right and left mouse buttons.
Click on the link below and you can test your system to see it your computer can run Oblivion. The site is safe and free most everybody here at Ironworks has used it.
After you click on the link the main page comes up and you need to click on
Select Product by pressing on the arrow to the right and find:
The Elder Scrolls Oblivion, and click on that. Then Click CAN you Run it?
and sit back for a minute or so while it checks your computer, when the test is over it tells you what upgrade is needed if any.
http://www.srtest.com/referrer/srtest