And some people have reported that Windows XP Fax Services causes their version of Outlook 2007 to behave sluggishly for whatever reason. If you don't fax in XP, you may be able to speed up Outlook by removing that feature. (To remove it, choose Control Panel -- Add or Remove Software -- Add/Remove Windows Components.)
Along the same lines, a number of users say the Business Contact Manager seriously slows down Outlook 2007, so if you have that installed, try uninstalling it using the same procedure.
Finally, check your RSS feeds. Outlook's RSS Feeds editor is a great feature, but using it can significantly slow things down. It comes preconfigured to receive a number of feeds that you may or may not want to receive. And over time, you may have subscribed to feeds you no longer read.
Select Tools -- Account Settings and click the RSS Feeds tab. You'll come to a screen like the one shown above. Scroll through your list of feeds. For the ones you no longer want, highlight them and select Remove. When you're done, click OK.
Annoyance No. 2Outlook's attachments make it massively bloated. If you regularly send and receive attachments, your Outlook .pst file can quickly become massively bloated. It's pretty easy for your .pst file to quickly get to 250MB or more, and I've known people whose files range up to 1GB and beyond. Among other problems, this slows down the speed at which Outlook loads and can lead to instability.
How to fix it: It's time to put Outlook on a diet. First, find out where the fat is. Outlook 2007 has a very useful folder called "Larger Than 100 KB." Find it underneath Search Folders in your list of Outlook folders. As the name implies, it lists all e-mail messages that are larger than 100KB. By default, they should be listed with the largest files first, but if not, click the Size heading in the folder until you get them listed that way.
Now that you can see the largest e-mails, start trimming. If you're like me, you'll be surprised how many of the e-mails with attachments you no longer need; delete those. If you need the attachment, but don't need the accompanying e-mail, save the attachment to disk, then delete the e-mail.
If the opposite is true -- you want to save the e-mail but not its attachment -- you can save space by either saving the attachment outside of Outlook or deleting it altogether. First, save the attachment to disk. Then open the e-mail, right-click the attachment and choose Remove. The attachment will be deleted from Outlook, but the e-mail itself will remain.