With the folder open where htc_fastboot.exe is located (looks like you named the folder "RUU"); hover your mouse over the folder. Press Shift + right mouse button, which will bring up a pulldown menu. Select "Open command window here". In the command window, enter the commands as indicated in the guide.
You can use the SD card method also. But if you're tinkering with these devices, it's a good idea to know how to use fastboot.
First of all, that isn't a kernel. It's kernel source code, and only useful to developers. It's not useful to you in any way, and doesn't have anything to do with your question/issue.
You won't find the Euro RUU 6.12.401.4 posted on the HTC website (or an exe format), if what is what you are looking for. Which is why you have been referred to the RUU zip in ckpv5's post.
Your CID (11111111) is known as SuperCID. It means you will bypass any CID check. Somewhat obvous, this has lots of advantages. Just make sure you only flash things which you are instructed to flash. Since flashing things like RUU/firmware with s-off (and bypassing the safety checks like CID) can result in damage, if you don't know exactly what you are doing.
---------- Post added at 11:09 AM ---------- Previous post was at 10:58 AM ----------
You can't trust those apps. They just report what is listed for CID in the build.prop, which is easily modified; and may therefore not correspond to the actual CID (what is checked for RUUs, etc.).
You need to check CID using command: fastboot getvar all
Or in your case, it is reporting SuperCID (11111111) on the bootloader screen, which is also trustworthy. But superCID is the only CID that is reported on the bootloader screen (other CID's, this line is skipped or blank in bootloader).
Oh thank you very much, it all worked out fine using the command prompt. I guess I shouldn't have trusted that CID Getter app after all... Anyways thanks a lot guys, however i've encountered a different issue with the top speaker being not as loud and tried cleaning with a toothbrush and when it didn't help i removed the cover for the top speaker and it was still quiet. I guess this is more of a hardware problem and not for this thread.