nor which Operating System you are using, so it is impossible to give detailed answers.

Here's a generic answer to the low disk space problem. If this is Windows XP disable System Restore, then re-enable it. This will delete all the System Restore back up files, but only do this if your system is otherwise working well.

Your second problem. You should also have Internet Explorer on your account. Did you check the Start Menu?

If nothing is there, find the shortcut from one of the other accounts, and drag it to the All Users Start Menu folder.