If you have not made the switch to Office 2007 from earlier version's and you receive documents that you cannot open ( such as doc x ) you will need the Microsoft Office Compatibility Pack for Word , Excel & PowerPoint 2007 File Formats.
As usual make sure you read the instructions before installing.
Sometimes you will can experience problems with your e mail client that will result in you needing to perform some maintenance to get it to work the way it should.
If your sent box becomes too full you can experience difficulties in sending mail.
You should create a new folder in your email client and move your old sent items into this if you really need to keep these.
If your sent box is too full it can result in multiple copies of emails being sent if the sent box is too full.
Also check if your mail client has an archive function ( such as outlook ) which should be run on a regular basis.
Last thing is to adjust your virus scanner to NOT scan e mails that you are sending only one's that come in.
I have seen a few people lately that have had their computers infected with virus's , spyware , malware.
There is a common theme in all these cases apart from the users behavior that caused them to become infected.
They had not kept up to date with Windows Update.
Windows Update is your first line of defence and automatic updates should be turned on.
Why are Windows Updates so critical to the prevention of virus's and infections in computers?
Virus's are written to exploit vulnerabilities in the operating system.
Windows Updates are released to amongst other things patch vulnerabilities in the operating system.
Therefore it makes sense to keep Windows Update's automatic update turned on along with your anti virus solution so that they can assist keeping malware etc at bay.
However remember it is also your actions that can help you not get infected as I have previously posted