| hxh | Microsoft Help 2 Merged TOC |
| hxi | Microsoft Help 2 Compiled Help Index |
| hxq | Microsoft Help 2 Query Data |
| hxr | Microsoft Help 2 Combined Attribute Index |
| hxw | Microsoft Help 2 Merged Index |
| hy1 | Corel Ventura Publisher Hyphenation Algorithm Data |
| hy2 | Corel Ventura Publisher Hyphenation Algorithm Data |
| hy3 | Hy-Tek Team Manager Data |
| hyb | HYB Hybrid Data |
| hyc | Corel WordPerfect Internal Data |
| hyd | MARIN Hydrodynamic Database File |
| hyp | HyperLynx BoardSim PCB Layout |
| hyq | CARE-S Depth Hydrographs for Gauged Pipes |
| hyv | Team Manager 1 Meet Setup File |
| hzd | SeisWorks Horizon Datafile |
| hzf | Neosat Fixes |
| hzn | Observer Pro Horizon Data |
| i2g | Intergeo I2G Geometric File |
| i5d | IUCLID5 XML Backup |
| i5z | IUCLID5 Export File |
| ia6 | IApproach Work Data |
| iab | DB/TextWorks Image Annotation List Backup |
| iab | Iomega Automatic Backup Data |
| iad | Symantec Patch Management Solution Data |
| iadpage | iAd Producer Page Template |
| iak | Mail.dat Information Access Key |
| ias | Intermodulation Analysis System Data |
| iati | International Aid Transparency Initiative Data |
| iaw | ImageAMMO Wrapper |
| ibak | Password Safe Intermediate Backup Archive |
