Is it all right to use powerpoint images on your website? For example, If I draw an arrow using the shapes tool, can I then cut the image from the powerpoint and save it, Then use it on my website?
Yes, you may. I contacted Microsoft support and they confirmed this. However, I don't know how much trust I would put into a chat representative for legal concerns. So, I've provided some more information...
Here is an excerpt from Microsoft's own website:
Additionally, here is an excerpt straight from PowerPoint 2007 EULA:
You may find out additional details here. For any further inquires I was suggested to contact microsoft directly, in writing, at:
One Microsoft Way
Redmond, WA 98052-6399
To expand upon Johannes' answer, a simple arrow like you describe in your question is not likely to pass the threshold of originality.
The details vary between jurisdictions, but for example, the Compendium of U.S. Copyright Office Practices states, in section 503.02(a), "Minimal standards: pictorial or graphic material":
Thus, you can safely use your arrow without having to worry about copyright issues. Of course, if it was a really fancy arrow, with a substantially original design, the situation might be different.