NOTE Before Continuing:

OfficeAdapterDecoder is NOT recommended for use.. its design requires fundamentally unsafe configuration (including that laid out in this article)

Please see INFO: OfficeAdapterDecoder Design Implications

Support and engineering strongly recommend not using this feature, and using the OfficeDecoder instead

Getting our OfficeAdapterDecoder component (see introductory KB article here) to run under IIS requires additional permissions. Specifically, it uses COM to interact with MS Office behind the scenes.

So, you need to change the COM security for the MS office applications (you must follow this for each application being authorized)

1. Start > Run > dcomcnfg (or “mmc -32? and then add the Component Services snap-in manually if you can’t find the app under step 3)
2. Navigate to Component Services > Computers > My Computer > DCOM Config
3. Locate the MS application giving you trouble (eg: "Microsoft Excel Application" for Excel or "Microsoft Word 97 – 2003 Document" for Word)
4. Right click > Properties
5. On the security tab: Select Customize under Launch and Activation Permissions and click Edit...
6. Add the account under which the site is running (eg: Network Service) and assign Local Launch & Local Activation permissions

Note: You do not want to use impersonate because then you'd need to ensure that any user being impersonated has these settings - the setup here implies not using impersonation - that you're giving the account running IIS the needed direct permissions.

Original Article:
Q10416 - HOWTO: Set Needed COM Permissions In IIS for OfficeAdapterDecoder