Outlook 2007 slow on closing and crashes on open

Your computer might be using caching. Can you tell me how much RAM you have on your computer? If you have 2GB of RAM i would recommend disabling the caching. This slows down the system quiet a bit (since it uses miliseconds instead of nanoseconds). Your computer is as fast as the slowest component.  I would also suggest defragging the drive.

Find SCANPST.EXE

In XP here: 'C:\Program Files\Common Files\System\MSMAPI\1033'
In Vista here: C:\Program Files\Microsoft Office\Office12

Close Outlook and run SCANPST.EXE

Restart machine

Open Outlook (you may have to wait for it to sync folder)

click on Tools \ Options
click on the Other tab and click the AutoArchive button.

Set archiving for your personal folder, the shorter the time, the better outlook will run. (I used 8 weeks, as I have outlook 2003 on XP with no issues, all mail is there if needed later)

click the button "Apply these settings to all folders now"

Shutdown Outlook 2007

Now Compact the PST File
Control Panel > Mail > Click Data Files. Then double-click “Personal Folders” and choose “Compact now”

When done, Restart machine and open Outlook 2007.

Worked wonders for me on Vista w/ 1gb ram