By default, X1 is able to index Excel files that have cells formatted using the general format and not cells that have been formatted using the number or currency format (for example).
However, X1 has the ability to utilize IFilters. When you install MS Office, a related IFilter for Excel should have also been installed. Telling X1 to use the MS Office IFilter may solve this issue.
To tell X1 to index your Excel files using an installed IFilter, perform these steps:
1. In X1, go to Tools > Options > Files > More Indexing Options > Specify File Types
2. In the "Additionally index all files with these extensions:" dialog, enter: XLS
3. Click Close, then OK
4. At this point, X1 needs to reindex the XLS files, so you've got a couple of options:
c. Clear and rebuild your index using Tools > Options > Indexing > Clear Index Files - note, that rebuilding includes
Once these XLS files have been reindexed, you may be able to perform searches against your Excel files that have cells formatted using the number/currency format (for example).
Please note: Because there are different versions of the IFilter installed, the above instructions may not always work.