[OnePlus Nord N200 5G] Winnower Amber:
Hey there. i'm a new XDA Member myself. i've been mostly stalking these forums for the N200 Ever since people started the root phase and twrp projects for codename HOLI. but i'm here to convert @summersofar's guide in order to make it more comfortable for windows users... (Credit to the people who helped make this happen. i take no credit as i am only posting this guide for windows users.)

Now lets get on with the process.

Requirements: Your Bootloader MUST Be unlocked. not just oem Unlocking enabled. NO. that only sets a flag in the bootloader telling the chip that the board can be unlocked. 2nd, you must have sim unlocked your phone in order for the oem unlocking option to appear, Be it t-mobile customer support via 611. or try twitter. there have been cases where users have gotten a free sim unlock from tmobile if you're a veteran customer (Veteran implies you've been with them for a couple of years now and they trust you. this isn't always guaranteed but its worth a shot honestly.) Twitter support will do. (Then unlock the bootloader permanently from oneplus's unlock token website and apply the unlock. they'll get back to you in7 business days.)

Now onto the actual process...

Make sure you first extract your stock image, You can do this by using a well known program called Payload Dumper Go. Note: you no longer need to do any sort of Mumbo jumbo in order to actually extract your stock img. You can download the stock image directly from Oneplus's support website located Here.

Step 1> Enable USB Debugging in the developer options and connect your phone. wait a couple of seconds and authorize the fingerprint on your devices screen. We can move onto step 2.

2>

/Next reboot into fastboot by typing the command below.\

fastboot reboot fastboot

3> Copy and paste these commands in cmd. (MAKE SURE YOUR COMMAND PROMPT DIRECTORY IS SET IN THE LOCATION WHERE YOUR EXTRACTED PAYLOAD FILES ARE!, or else you'll get an error saying the file cannot be found or executed.

fastboot delete-logical-partition system_a-cow
fastboot delete-logical-partition odm_a
fastboot delete-logical-partition system_a
fastboot delete-logical-partition system_ext_a
fastboot delete-logical-partition product_a
fastboot delete-logical-partition vendor_a
fastboot create-logical-partition odm_a 0x37ED000
fastboot create-logical-partition system_a 0x6342E000
fastboot create-logical-partition system_ext_a 0x55225000
fastboot create-logical-partition product_a 0x6BD93000
fastboot create-logical-partition vendor_a 0x3ED70000
fastboot flash boot boot.img
fastboot flash dtbo dtbo.img

Then reboot into fastboot once all those commands Above are executed..

fastboot reboot fastboot

Next we'll actually tell the bootloader to CREATE And delete the partitions. in order to finalize the process.

fastboot flash --slot=all boot boot.img
fastboot flash --slot=all dtbo dtbo.img
fastboot flash --slot=all abl abl.img
fastboot flash --slot=all bluetooth bluetooth.img
fastboot flash --slot=all devcfg devcfg.img
fastboot flash --slot=all dsp dsp.img
fastboot flash --slot=all featenabler featenabler.img
fastboot flash --slot=all hyp hyp.img
fastboot flash --slot=all imagefv imagefv.img
fastboot flash --slot=all keymaster keymaster.img
fastboot flash --slot=all logo logo.img
fastboot flash --slot=all modem modem.img
fastboot flash --slot=all qupfw qupfw.img
fastboot flash --slot=all tz tz.img
fastboot flash --slot=all uefisecapp uefisecapp.img
fastboot flash --slot=all xbl_config xbl_config.img
fastboot flash --slot=all xbl xbl.img
fastboot flash --slot=all core_nhlos core_nhlos.img
fastboot flash --slot=all oplusstanvbk oplusstanvbk.img
fastboot flash --slot=all rpm rpm.img
fastboot flash --slot=all vendor_boot vendor_boot.img
fastboot flash odm odm.img
fastboot flash system system.img
fastboot flash system_ext system_ext.img
fastboot flash product product.img
fastboot flash vendor vendor.img
fastboot flash --slot=all vbmeta vbmeta.img
fastboot flash --slot=all vbmeta_system vbmeta_system.img

Once thats been done. just go ahead and execute the commands below to boot to the RECOVERY this time.

fastboot reboot recovery

Once done. Wipe your user cache and settings. you have to press two buttons to execute this. Enjoy a fully (Clean?) stock rom.

The issues and problems post installation can be found in @summersofar's guide Here.

Too long to type out all of them.