Mystiques, it's normal to have multiple iexplore.exe processes when running Internet Explorer 7 or 8. IE8 will start one iexplore.exe instance for the browser and an additional iexplore.exe for each tab or tab group. If you are on IE8 and have 4 iexplore.exe processes running, that should be 3 tabs or tab groups currently open. This is a good feature because one tab/tab group can crash and not take any others with it.
How much memory are these processes using? IE8 should not be that much of a memory hog.
BTW, I'm assuming that you are referring to Internet Explorer's process which is called "iexplore.exe", not "iexplorer.exe" (with an 'r' at the end). If you actually have processes named "iexplorer.exe", that is probably malware.