Yes, Siebel 8.1 & Siebel 8.2 supported with IE 9 (32-bit).
For more information visit the follwoing:
You need to make several changes in IE Settings and in Seibel Internet browser settings.
Windows 8 has not been certified yet for Mobile or Developer Web Client, it is planned for the second half of 2013 per doc ID 1490054.1 on Oracle Support. Document below will be updated when Windows 8 has been certified: