In no particular order:
Tip: Insert your Office 2010 CD into the appropriate drive bay before the next installation attempt.
Tip: Access either of the following KB articles via IE (32-bit) only, run the Fix It & reboot before the next installation attempt:
• Error code "0x80070646," "646," or "1606" running Windows Update
• You receive an "Error 1606" error message when you try to install or remove a Microsoft program
[ignore title, error number, etc.]
Tip: If no joy, see if you can download the "fullfile" version of the update(s) via Microsoft Download Center
or Microsoft Update Catalog
and then install it/them manually.
Tip: If still no joy & you're running Windows 7 or Vista, temporarily disable (turn off) User Account Control (UAC) before the next installation attempt.
• Guided Help: Adjust User Account Control settings in Windows 7: Guided Help: Adjust User Account Control settings in Windows 7
• Turn User Account Control on or off (Vista) Turn User Account Control on or off
NB: Remember to turn UAC back on afterwards!