Sihost.exe is a Windows shell-related program, such as the graphical processing interface we see, etc. If this file is lost or damaged, it will return to the string command interface, which is the DOS interface, just like the following picture:
In addition, damage to the sihost.exe file may also result in a blue screen on the system.
To fix this problem, you can only find a complete file to replace the damaged file.
However, if you say that both explorer.exe and sihost.exe have problems at the same time, then I can be sure that your system is infected by a virus, because these two files are most easily injected or modified by the virus, so it is best to find an anti-virus software to remove the virus from the system.