I have the EA game Battlefield: Vietnam, it doesn't play well with Windows 11.

Have you tried running Battlefield: Vietnam in Compatibility Mode in Windows 11?  You can set Windows 11 to run the game in the version of Windows that worked best for your title.  Below you will find a hyperlink that can step you though the process:

https://www.online-tech-tips.com/computer-tips/run-older-programs-in-compatibility-mode-in-windows-11-10/ 

I hope this helps.

since Battlefield Vietnam is such a rare played battlefield I do not have alot of knowledge of it but I'm pretty sure it could be made to work using community made fixes.

I suggest joining the last remaining battlefield Vietnam clan, named helloclan

here is discord or website they'll probably be able to help you.

https://www.helloclan.eu/resources/categories/2/

https://discord.gg/UVzSQNBPm8

Well it seems that didn't help, I rifled through all the compatibility modes with bupkus.

Well here is what I want to do now. My old laptop(a hand-me-down from my older brother(seems he's all  the time doing that)), had Windows 7 installed when he acquired it. I was at his house and decided to install Windows 10 on it. BFV seemed to work fine on Win7 and Win10, both. Anyway, I had gotten my current rig about a year ago. It was faster had SSD and more mem plus it was faster. Anyway, I hardly used the old one. But I was playing a few online games on the new one. I wanted to play BF Vietnam on the new laptop so I installed and no go. Not even a start up. Along the way I ran out of room on both laptops. So I just kept playing the online games which were on Steam. The new laptop had Windows 11 so I was happy and it did play games I enjoyed, well. I just decided to go ahead and get a new drive for the old one and install Win7 or reinstall it. So that is what I am doing now. Should no more that a couple of days, and I had to reinstall Win10 so I can reinstall Win7. I just don't want to run into license and activation issues.

There is NO compatibility mode for Windows 11 and trying all the other OS variants don't work.

I think I found the solution. Your computer needs a drive other than the C:\ (system drive) working with Windows 11. On the C:\ Drive I couldn't get BFV to start let alone play in any compatability mode. I believe I tried them all. I have a brand new desktop, Set CLX, and can easily play high demand games, BF1 for example. Same with my Lenovo Legion laptop. I also have an old outdated Lenovo laptop which plays BFV on Windows 10, this laptop not being relevant. I have multiple external hard drives formatted to NTFS. This is the only option to get Windows 11 to recognize the drive(s). Also if there is another internal drive aside from C:\, you can try it on that one. Keep in mind all the tricks and steps to get BFV installed and also patched. Patch to which version you prefer, I just did a fresh install on a external for the laptop. It worked perfectly. Also keep in mind all Mods you care to install, just do as instructed. This should get you up and running on a primary system. I have two computers and I wanted to network them, and run the server on one and play on the other. My desktop monitor is a Hisense TV. If you have any questions about installing on the external/other internal drives, reply to my post, I will be notified. I won't address compatibility issues, for those you'll be on your own. I have seen a few in this thread. Read the whole thread. Cheers and Bon Chance!