Hi again
First of all, go to Microsoft's site and download the installation program for I.E. you can find it here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=1e1550cb-5e5d-48f5-b02b-20b602228de6&DisplayLang=en
Download this file and then run it. It will connect to Microsoft's site and download and install the latest version of I.E. for you.
If this does not work (i.e. you are unable to install it), then you should try to repair I.E.
To repair I.E. click Start>Settings>Control Panel and open Add/Remove Programs. If you scroll down the list of installed programs you should see an entry for Internet Explorer. Double click it and choose repair.
If this does not work then you should examine any add-ons for I.E. These are often referred to as BHO's or Browser Helper Objects, but can also be activeX controls and also Toolbars. You can locate these by clicking Tools>Internet Options>Programs and click Manage Add-ons. After a few seconds a list of add-ons will appear. You should disable anything you are not sure of.
Also, you did not say specifically, but have you checked the entries in the Advanced tab of the Options dialog and made sure that SSL 2 and 3 are checked. You will not be able to access https sites if they are not.
Good luck