Is there any tool to open and process MCD12Q1
(modis landcover product)
Apparently ENVI doesn't work for this.
Most packages can handle TIFFs and they're easy to work with.
Use the MODIS Reprojection Tool (MRT) to convert HDFs to TIFFs. You can select the coordinate system and fields you want to extract from the HDF. You can do them one at a time or you can use the tool to create parameter files to mosaic and project multiple scenes for batch processing.
https://lpdaac.usgs.gov/tools/modis_reprojection_tool
The MRT tool is a little finicky. You need to have both MRT and Java installed to a folder on your drive without spaces. I suggest reinstalling (or installing) Java and MRT to C:/programs/java and C:/programs/MRT. It can have problems searching for them when they are located in Program Files.
ArcMap can handle HDFs, too.
Above answer is the perfect method to do it.But, if you work with ERDAS, use import and the MODIS file type is MODIS EOS HDF format(select from drop down list). you can convert its to another format.Also you can use gdal to do it.(in R , the package is gdalUtils)