Why my pc still can't update to windows 11 from windows 10?

Your HP ProDesk 400 meets the performance requirements for Windows 11, but the reason it's not showing the upgrade in Windows Update is almost certainly Microsoft's official hardware restrictions as follows:

• TPM 2.0: Your model likely has TPM 1.2 or no TPM at all.
• Secure Boot: May be disabled in BIOS.
• CPU: Intel i5-6500 (Skylake) isn’t on Microsoft’s “supported CPUs” list, even though it's powerful enough.

That's why this pc can't update to Windows 11 from Windows 10.

No worries. WinBoootMate software can create a bootable USB for Windows 11 that removes TPM/Secure Boot/CPU checks.

Step 1: Go to Microsoft's Windows 11 download page and get the ISO file.

Step 2: Insert a USB drive (8GB or larger) and select:

• Boot selection → Choose your Windows 11 ISO.
• Partition scheme → GPT (if your disk is GPT) or MBR (if MBR).
• Target system → UEFI (non-CSM) or BIOS depending on your setup.

Step 3: When you click Start, it will show a prompt:

✅ Remove requirement for 4GB+ RAM, TPM 2.0, Secure Boot, CPU check.

✅ Optionally disable account sign-in requirements.

After creation, run setup.exe from the USB while inside Windows 10 (don’t boot from USB).

Step 4: Choose the option "Keep personal files and apps" for update from Windows 10 to Windows 11.