The current Salesforce.com Outlook integration tool is not working on 64-bit windows systems, Vista and Windows 7.

There is currently an item posted on the AppExchange to support the 64-bits version. This idea is under consideration but will probably not be in the Summer '10 release which is coming in the second week of July. 

There is however a workaround;

 The Salesforce.com Outlook integration installer does not include the required DLLs necessary to drive the install being "msvcp71.dll" and "msvcr71.dll".

1. Find these DLLs, they are somewhere on your harddrive (or download them here and here
2. Go to Control Panel and disable UAC (User Account Control Settings) by typing UAC in the search box of the Control Panel. 
3. Uncheck the box after the prompt to disable UAC
4. Reboot Windows
5. Run the installer for the Salesforce.com Outlook Edition, it should create the C:\\Program Files (x86)\\salesforce.com\\O3\\ directory.
6. Copy the two DLLs described above into this directory after the install
7. Run Outlook, the tool should now work, enter username and password and configure your settings
8. You can re-enable UAC through Control Panel as per Step 2 and reboot Windows

Hope this helps until the Salesforce.com Outlook Edition installer supports 64 bit.