According to the information we have, this is an SFF case. An Intel i5-8500 is installed as the CPU.

An upgrade to Windows 11 for the "EliteDesk 800 G4" is possible under certain conditions. ### Requirements - The PC must have an Intel 8th Generation Core processor or newer, which is the case with the EliteDesk 800 G4, as it is often equipped with Core i5 or i7 processors. - TPM 2.0 must be activated in the BIOS. - Windows must be installed in UEFI mode and Secure Boot must be activated. ### Checking the compatibility - Use the PC Health Check app from Microsoft to check the compatibility of your system. In most cases, this app shows whether the EliteDesk 800 G4 is compatible with Windows 11. ### Potential problems - There are reports that older HP computers, even if compatible, can cause problems such as blue screens (BSOD) when upgrading to Windows 11. It is advisable to install all the latest drivers and BIOS updates before upgrading. If all requirements are met and the check shows no problems, the upgrade to Windows 11 should be possible without major difficulties.