Whilst I really do not recommend anyone doing this (tainting your pristine Linux box with tainted Windows applications hehehe) but if you really do not have a choice, here is a tutorial on how to install Microsoft's Internet Explorer using IEs4Linux. The tutorial is written for Ubuntu from Dapper Drake, Edgy Eft and Feisty fawn.

Whilst I have not tried it yet so I cannot say how easy and stable it is but I can attest on how easy it is to use Codeweaver's CrossOver Office Professional, but that will set you back for a couple of dollars.