Hi Nanookz,
Please try the following methods to narrow down the cause of the slow performance:
1. Try start your Outlook in
safe mode, and check the launch speed;
2. Check if you have enabled
Cache Exchange Mode, if no, enable it and try start Outlook, and check the launch speed;
3. Create a new profile with no email account, try start Outlook, and check the launch speed;
4. Create a new Profile with the other email account, try start Outlook, and check the launch speed;
5. Try configure your computer to reboot in
clean boot mode, and try start Outlook, and check the launch speed;
6. Try Create a new Windows profile, try start Outlook, and check the launch speed;
.
For the query about Microsoft Online Services Sign-in Assistant (MOS SIA), we'd recommend you to visit the Office 365 Community at
http://community.office365.com/en-us/forums/default.aspx
BTW, as we can learn from the download page, for users who are installing Office 365 by means of the Office 365 Desktop Setup application, this download is not necessary, because the MOS SIA is installed as part of the Desktop Setup process.