What does your IT-guy say?
With company PC's my recommendation is to NOT spend any time looking for the cause, but just follow the procedures for fixing it: a clean install of Windows and applications. Data should already be on the company server, so that's no problem.
This is fast, cheap, routine and sure to work.
Oh... how do I explain this...
One of my colleagues has this problem - when she receives an e-mail, for example 3 pages long. She doesn't receive the whole text. So she receives the e-mail. It's size is the same as the size in other people's "sent items" folder (so it should be the whole e-mail), but when she open it, only as much text as one maximized window can contain can be viewed. Like she's not able to scroll down the page, to view the rest of the e-mail. And when she writes an e-mail, it happens the same thing. Outlook adds signature automaticly, so when she forwarded me an e-mail, that had the same problem, there were like 6 lines for the signature, and 6 lines from the e-mail disapeared. But the size remains the same, like it should be the whole one. I don't know if you understand what I mean. Imagine it like you open a several pages word document, and then you cannot scroll down to read the whole text. You can read only this, that you have on screen the moment you open it. I tried to find something over the internet about it, but I had no success. Can anyone help?