0XC026230B: Fix invalid active region error on Windows

This error pops up when Windows can't set a custom display resolution because the active region (the part of the screen actually showing content) is outside the monitor's limits.

When this error hits

You're trying to set a custom resolution — maybe for a game that wants a weird aspect ratio, or you're forcing 1440p on a 1080p monitor. You go into NVIDIA Control Panel or AMD Adrenalin, punch in the numbers, and boom: 0XC026230B. Screen stays black, nothing changes. The error message says the active region is invalid.

What's actually happening here is that the video signal you're asking for has a visible area — the part with pixels — that doesn't fit inside the monitor's maximum blanking or sync timing limits. Think of it like trying to squeeze a 16:9 movie into a 4:3 frame: part of the image would hang off the edge. The GPU says "nope, won't do it."

Why the GPU cares

Every monitor has a range of horizontal and vertical pixels it can actually display. Those are stored in the EDID (Extended Display Identification Data) — a small chunk of data the monitor sends to Windows. When you set a custom resolution, the GPU checks if the active region (the horizontal and vertical resolution you picked) plus the blanking areas (invisible borders around the image) don't exceed the monitor's limits. If they do, you get 0XC026230B.

The trigger is almost always one of three things:

Wrong timing parameters — you copied someone else's resolution settings without adjusting refresh rate or blanking
Monitor EDID caps — the monitor's internal database says "max 1920x1080" and you're asking for 2560x1440
Driver version bug — rarely, a corrupted driver misreads the EDID

The fix

Skip the generic "update your driver" advice — that rarely helps here. The real fix is to either adjust the custom resolution timing or override the EDID entirely.

Step 1: Check your monitor's native resolution

Open Windows Settings > System > Display > Advanced display. Note the Desktop resolution and Active signal resolution. They should match. If they don't, that's a clue the GPU is already fighting the EDID. Write down the native resolution.

Step 2: Use CRU (Custom Resolution Utility) to see the real limits

Download CRU — it's free, no install needed. Run it, select your monitor from the dropdown at top. Look at the "Extension blocks" section. Every monitor has a set of standard resolutions it reports. The highest one shows the pixel clock limit (in MHz). For example, a 60Hz 1080p monitor usually has a pixel clock around 148.5 MHz. If your custom resolution needs a pixel clock above this, you'll get the error.

What you need: pixel clock of your custom res must be at or below that limit. Formula: (horizontal total pixels) × (vertical total pixels) × (refresh rate) = pixel clock in Hz. Divide by 1,000,000 for MHz.

Step 3: Reduce the blanking timings

If you're close to the limit, reduce the front porch, sync width, and back porch values. In CRU, click "Add" under Detailed Resolutions, pick "Automatic - LCD Reduced Standard". This cuts blanking to the minimum the GPU still accepts. Set your target resolution and refresh rate. Click OK, then run restart64.exe in CRU's folder to apply.

Why step 3 works: by using LCD Reduced Standard, you lower the total horizontal pixels (active + blanking) so the pixel clock drops below the monitor's ceiling. The error goes away because the active region now fits.

Step 4: Override the EDID if nothing else works

Open CRU again, click "Export" to save your current EDID as a .bin file (backup). Then delete all entries under "Detailed Resolutions" and "Standard Resolutions" except the one you just created. Click OK, restart the driver (restart64.exe). This forces Windows to only see your custom resolution. Warning: if you pick a resolution the monitor genuinely can't display, you'll get a black screen at boot — so have a second monitor or keyboard shortcut to safe mode ready.

What to check if it still fails

Monitor compatibility: Some cheap HDMI monitors lie about their pixel clock limits. Try a lower refresh rate (e.g., 50Hz instead of 60Hz) to drop the pixel clock.
Cable quality: HDMI 1.4 can't push 4K60. If you're using an old cable, switch to HDMI 2.0 or DisplayPort.
Driver version: NVIDIA 537.13 and AMD 23.9.1 introduced stricter EDID checks. Roll back to an older driver if you're stuck.
Check for corrupted EDID: Run edid-decode from a live Linux USB — if the EDID has checksum errors, the monitor hardware might be failing. That's rare but happens.