There must be something else blocking the old CPU, this from Copilot,
"
The **Intel Core i7‑2600** (and the 2600K) is **not officially supported** for Windows 11.
Here’s why:
- Microsoft’s official compatibility list only includes **8th‑generation Intel CPUs and newer**.
- The i7‑2600 is a **2nd‑generation Sandy Bridge processor** (launched in 2011), so it falls well outside the supported range.
- Even if your system meets RAM, Secure Boot, and TPM 2.0 requirements, the CPU itself blocks official eligibility.

**Workarounds:**
- It *is* possible to install Windows 11 on unsupported hardware by bypassing checks (using tools like Rufus or registry tweaks). Many users have done this successfully.
- However, Microsoft warns that unsupported installs may not receive updates reliably, and there’s no guarantee of long‑term stability or security.

**Bottom line:**
- **Officially:** No, the i7‑2600 is not compatible with Windows 11.
- **Unofficially:** Yes, you can force an install, but you’ll be running outside Microsoft’s support boundaries. "