From Identity Finder tech support:
The "common file types" list includes documents that normally contain searchable text. Identity Finder has internal (native) support for: PDF files, HTML files, RTF files, archived files (if "Compressed Files" are being searched), CSV files, Access DB files, OneNote files, and anything for which an i-filter is installed on the operating system. Starting with Windows 2000, i-filters are installed for all Microsoft Office files at the operating system level, including but not limited to Word, Excel and Powerpoint document formats. If you have other programs that have installed i-filters Identity Finder will automatically register those file types and search their text, if any exists, based on the text output of the registered i-filter.
Here are a list of file extensions that are natively supported by Identity Finder: 1st,asm,asp,aspx,bat,btm,c,cc,cmd,cpp,cs,css,cxx,def,dic,h,hpp,hxx,idl,idq,inc,inf,ini,inx,java,js,jsl,log,me,pl,rc,reg,rels,snippet,text,txt,url,vbs,wtx,xml,xsl,pdf,edn,fdf,xdp,xfd,xfdf,htm,html,rtf,gz,tar,z,rar,bz,bz2,tgz,tbz,tbz2,zip,csv,mdb,accdb,one
Here is a list of files that have operating system i-filter support (Office Documents): doc,dot,xls,xla,xlb,xlc,xld,xlk,xll,xlm,xlt,xlv,xlw,dif,slk,ppt,pot,ppa,pps,pwz
If Office 2007 is installed with Identity Finder 3.x, the following formats are supported, or if Identity Finder 4.x is used support is native for these extensions: docx,docm,dotx,dotm,xlam,xlsx,xlsm,xltm,xltx,pptm,pptx,potx,potm