| Extension | File Description |
| .BI7 | Uncommon Files |
| .BI8 | Uncommon Files |
| .BI9 | Uncommon Files |
| .BI? | Text Files |
| .BIA | Uncommon Files |
| .BIAR | Uncommon Files |
| .BIB | Text Files |
| .BIBTEX | Uncommon Files |
| .BIC | Game Files |
| .BID | Uncommon Files |
| .BIE | Uncommon Files |
| .BIF | Backup Files |
| .BIFF | Uncommon Files |
| .BIG | Game Files |
| .BIG5 | Uncommon Files |
| .BIGBLUEFON | Uncommon Files |
| .BIH | Uncommon Files |
| .BII | Uncommon Files |
| .BIJ | Uncommon Files |
| .BIK | Game Files |
| .BIL | GIS Files |
| .BILL | Uncommon Files |
| .BIM | Data Files |
| .BIMD | Uncommon Files |
| .BIN | Data Files |
| .BINS3 | Uncommon Files |
| .BINS4 | Uncommon Files |
| .BIO | 3D Image Files |
| .BIOT | Uncommon Files |
| .BIP | 3D Image Files |
| .BIQ | Uncommon Files |
| .BIR | Uncommon Files |
| .BIRD | Uncommon Files |
| .BIS | Uncommon Files |
| .BIT | CAD Files |
| .BITMAP | Uncommon Files |
| .BIU | Uncommon Files |
| .BIV | Uncommon Files |
| .BIW | Uncommon Files |
| .BIX | Game Files |
| .BIY | Uncommon Files |
| .BIZ | Page Layout Files |
| .BIZDESIGN | Uncommon Files |
| .BIZDOCUMEN | Uncommon Files |
| .BIZZARELOV | Uncommon Files |
| .BJ0 | Uncommon Files |
| .BJ1 | Uncommon Files |
| .BJ2 | Uncommon Files |
| .BJ3 | Uncommon Files |
| .BJ4 | Uncommon Files |
| .BJ5 | Uncommon Files |
| .BJ6 | Uncommon Files |
| .BJ7 | Uncommon Files |
| .BJ8 | Uncommon Files |
| .BJ9 | Uncommon Files |
| .BJA | Uncommon Files |
| .BJB | Uncommon Files |
| .BJC | Uncommon Files |
| .BJD | Uncommon Files |
| .BJE | Uncommon Files |
| .BJF | Uncommon Files |
| .BJG | Uncommon Files |
| .BJH | Uncommon Files |
| .BJI | Uncommon Files |
| .BJJ | Uncommon Files |
| .BJK | Uncommon Files |
| .BJL | Uncommon Files |
| .BJM | Uncommon Files |
| .BJN | Uncommon Files |
| .BJO | Data Files |
| .BJP | Uncommon Files |
| .BJQ | Uncommon Files |
| .BJR | Uncommon Files |
| .BJS | Uncommon Files |
| .BJT | Uncommon Files |
| Extension | File Description |
| .BJU | Uncommon Files |
| .BJV | Uncommon Files |
| .BJW | Uncommon Files |
| .BJX | Uncommon Files |
| .BJY | Uncommon Files |
| .BJZ | Uncommon Files |
| .BK | Data Files |
| .BK! | Uncommon Files |
| .BK$ | Uncommon Files |
| .BK0 | Uncommon Files |
| .BK1 | Backup Files |
| .BK2 | System Files |
| .BK3 | Uncommon Files |
| .BK4 | Uncommon Files |
| .BK5 | Uncommon Files |
| .BK6 | Uncommon Files |
| .BK7 | Uncommon Files |
| .BK8 | Uncommon Files |
| .BK9 | Uncommon Files |
| .BKA | Uncommon Files |
| .BKB | Uncommon Files |
| .BKC | Backup Files |
| .BKD | Uncommon Files |
| .BKE | Uncommon Files |
| .BKF | Backup Files |
| .BKG | Uncommon Files |
| .BKGND | Uncommon Files |
| .BKH | Uncommon Files |
| .BKI | Uncommon Files |
| .BKJ | Uncommon Files |
| .BKK | Uncommon Files |
| .BKL | Uncommon Files |
| .BKM | Data Files |
| .BKN | Uncommon Files |
| .BKO | Uncommon Files |
| .BKP | Backup Files |
| .BKQ | Uncommon Files |
| .BKR | Uncommon Files |
| .BKS | Settings Files |
| .BKT | Uncommon Files |
| .BKU | Uncommon Files |
| .BKV | Uncommon Files |
| .BKW | Uncommon Files |
| .BKX | Uncommon Files |
| .BKY | Uncommon Files |
| .BKZ | Uncommon Files |
| .BL | Uncommon Files |
| .BL0 | Uncommon Files |
| .BL1 | Uncommon Files |
| .BL2 | Uncommon Files |
| .BL3 | Uncommon Files |
| .BL4 | Uncommon Files |
| .BL5 | Uncommon Files |
| .BL6 | Uncommon Files |
| .BL7 | Uncommon Files |
| .BL8 | Uncommon Files |
| .BL9 | Uncommon Files |
| .BLA | Uncommon Files |
| .BLACK | Uncommon Files |
| .BLACKMORE | Uncommon Files |
| .BLANK | Uncommon Files |
| .BLAST | Uncommon Files |
| .BLASTER | Uncommon Files |
| .BLASTERBAL | Uncommon Files |
| .BLB | Data Files |
| .BLC | Uncommon Files |
| .BLD | Data Files |
| .BLD2 | Uncommon Files |
| .BLDITAL | Uncommon Files |
| .BLE | Uncommon Files |
| .BLEEP | Uncommon Files |
| .BLEND | 3D Image Files |
| .BLF | System Files |
| .BLG | Data Files |
| .BLH | Uncommon Files |
