System restore's size will depend on a few things:
-Size of your drive overall
-Size of your files
-How many restore points there are
Usually the restore points will automagially be created after updates, installs etc.
To change the values that system restore uses, go to control panel, system properties - then the system restore tab. On the tab you can change which drives system restore is monitoring and the overall space allocated.
You can 'clean up' unwanted restore points by selecting the clean up option on the hard drive, and under then advanced tab there is an option to get rid of all system restore points except for the most recent.
There is no reason for any individual to have a computer in his home.
President, Digital Equipment, 1977