| Extension | File Description |
| .COM2 | Uncommon Files |
| .COMBAT | Uncommon Files |
| .COMICSCART | Uncommon Files |
| .COMING | Uncommon Files |
| .COMMANDLIN | Uncommon Files |
| .COMMANDS | Uncommon Files |
| .COMMANDS2 | Uncommon Files |
| .COMMENTS | Uncommon Files |
| .COMMON | Uncommon Files |
| .COMMS | Uncommon Files |
| .COMPACT | Uncommon Files |
| .COMPANY | Uncommon Files |
| .COMPARE | Uncommon Files |
| .COMPARISON | Uncommon Files |
| .COMPAT | Uncommon Files |
| .COMPILERS | Uncommon Files |
| .COMPLICATI | Uncommon Files |
| .COMPOSER | Uncommon Files |
| .COMPPIANO | Uncommon Files |
| .COMPRESSIO | Uncommon Files |
| .COMPRESSOR | Uncommon Files |
| .CONCERTO | Uncommon Files |
| .CONFERENCE | Uncommon Files |
| .CONFIDENT2 | Uncommon Files |
| .CONFIDENTI | Uncommon Files |
| .CONFIGDBLI | Uncommon Files |
| .CONFIGS | Uncommon Files |
| .CONFIGURE | Uncommon Files |
| .CONNECTION | Uncommon Files |
| .CONSEQUEN | Uncommon Files |
| .CONSOLE | Uncommon Files |
| .CONT | Uncommon Files |
| .CONTENTS | Uncommon Files |
| .CONTENTSON | Uncommon Files |
| .CONTROL | Uncommon Files |
| .CONTROLPAN | Uncommon Files |
| .CONV | Uncommon Files |
| .CONVERSION | Uncommon Files |
| .CONVERT | Uncommon Files |
| .CONVERT2 | Uncommon Files |
| .CONVERTER | Uncommon Files |
| .COO | Uncommon Files |
| .COOKIES | Uncommon Files |
| .COOL | Uncommon Files |
| .COP | Uncommon Files |
| .COPIER | Uncommon Files |
| .COPIEREC | Uncommon Files |
| .COPPER | Uncommon Files |
| .COPYING | Uncommon Files |
| .COPYR | Uncommon Files |
| .COQ | Uncommon Files |
| .CORE | Uncommon Files |
| .CORELPROJE | Uncommon Files |
| .CORELSHOW | Uncommon Files |
| .CORRECT | Uncommon Files |
| .CORRECTION | Uncommon Files |
| .CORTOUCHKA | Uncommon Files |
| .COS3 | Uncommon Files |
| .COSMO | Uncommon Files |
| .COSMO2 | Uncommon Files |
| .COSMO3 | Uncommon Files |
| .COSMO4 | Uncommon Files |
| .COSMO5 | Uncommon Files |
| .COSTS | Uncommon Files |
| .COT | Uncommon Files |
| .COU | Uncommon Files |
| .COUNT | Uncommon Files |
| .COUNTER | Uncommon Files |
| .COW | Uncommon Files |
| .COY | Uncommon Files |
| .COZ | Uncommon Files |
| .CP0 | Uncommon Files |
| .CP1 | Uncommon Files |
| .CP2 | Uncommon Files |
| .CP3 | Uncommon Files |
| Extension | File Description |
| .CP4 | Uncommon Files |
| .CP5 | Uncommon Files |
| .CP6 | Uncommon Files |
| .CP7 | Uncommon Files |
| .CP8 | Uncommon Files |
| .CP9 | Uncommon Files |
| .CPAN | Uncommon Files |
| .CPAO | Uncommon Files |
| .CPB | Uncommon Files |
| .CPICS | Uncommon Files |
| .CPJ | Uncommon Files |
| .CPM | Uncommon Files |
| .CPO | Uncommon Files |
| .CPT6 | Uncommon Files |
| .CPTHEME | Uncommon Files |
| .CPU | Uncommon Files |
| .CPV | Uncommon Files |
| .CPW | Uncommon Files |
| .CPZ | Uncommon Files |
| .CQ | Uncommon Files |
| .CQ0 | Uncommon Files |
| .CQ1 | Uncommon Files |
| .CQ2 | Uncommon Files |
| .CQ3 | Uncommon Files |
| .CQ4 | Uncommon Files |
| .CQ5 | Uncommon Files |
| .CQ6 | Uncommon Files |
| .CQ7 | Uncommon Files |
| .CQ8 | Uncommon Files |
| .CQ9 | Uncommon Files |
| .CQA | Uncommon Files |
| .CQB | Uncommon Files |
| .CQC | Uncommon Files |
| .CQD | Uncommon Files |
| .CQE | Uncommon Files |
| .CQF | Uncommon Files |
| .CQG | Uncommon Files |
| .CQH | Uncommon Files |
| .CQI | Uncommon Files |
| .CQJ | Uncommon Files |
| .CQK | Uncommon Files |
| .CQL | Uncommon Files |
| .CQM | Uncommon Files |
| .CQN | Uncommon Files |
| .CQO | Uncommon Files |
| .CQP | Uncommon Files |
| .CQQ | Uncommon Files |
| .CQR | Uncommon Files |
| .CQS | Uncommon Files |
| .CQT | Uncommon Files |
| .CQU | Uncommon Files |
| .CQV | Uncommon Files |
| .CQW | Uncommon Files |
| .CQX | Uncommon Files |
| .CQY | Uncommon Files |
| .CQZ | Uncommon Files |
| .CR | Uncommon Files |
| .CR$ | Uncommon Files |
| .CR0 | Uncommon Files |
| .CR1 | Uncommon Files |
| .CR3 | Uncommon Files |
| .CR4 | Uncommon Files |
| .CR5 | Uncommon Files |
| .CR6 | Uncommon Files |
| .CR7 | Uncommon Files |
| .CR8 | Uncommon Files |
| .CR9 | Uncommon Files |
| .CRA | Uncommon Files |
| .CRACK | Uncommon Files |
| .CRACKING | Uncommon Files |
| .CRACKPOTY | Uncommon Files |
| .CRACKZBYMA | Uncommon Files |
| .CRAM | Uncommon Files |
| .CRASH2 | Uncommon Files |
| .CRATE | Uncommon Files |
