What is sysmain, and why does it sometimes use a bunch of CPU? Can I disable it, and what happens if I do?

I have Windows 11 on a 15 year old computer with an SSD. Don't let them fool you.

I am not very technical but if my SysMain is using 96 percent of my CPU, how can it be optimizing my conputer. I have a small HP All in One with I think 4MB of Ram (maybe GB) and it is running so slow as to be unusable. It happened very suddenly, right after a MS update. I think the update reset something and now my computer is not useful to me. If I disable SysMain to see if it works better again, then would it be bad to leave it disabled? I dont do a lot of heavy computing or games or anything. Mostly correspondence and reading email. Do I need professional help?

Sandra - I had the exact thing happen about the same time so it had to be a MS update that made it happen. I disabled SysMain and that did NOT help. It took me all these months of trying many things and my disk still ran at 100%, opening anything was frustrating. BUT, I finally found an answer (a simple answer).
TRY THIS . . .
Windows key > Settings (cog button) > System > Notifications > uncheck 'Show windows tips' (or a version of that). Actually I just turned off all notifications as I found I didn't need them. And, walaaa, I have my computer back.

Good morning,

Sorry if I don't write correctly, I use Google translate, because I don't speak English.

I have a question, many people say that for an nvme hard drive like mine (7350 writes, 6000 reads), it is better to disable SysMain, because my hard drive is faster than my ram (4000Mhz).

Is this true or false?

Good day.

Tiny11 will work on these older computers. Put it on a stick and use it. It would be either MBR or GPT though. Make sure that you know what your computer uses. Device Manager>>Hard drive>>Properties>>Volume tab>>Populate button. I usually will change it to UEFI in the bios and then it will create the GPT hard drive partition table. If you don't have UEFI then use Legacy or ACHI but then you would have to make your hard drive partition MBR. Legacy and ACHI are pretty old now. The first open source UEFI implementation, Tiano, was released by Intel in 2004 so that would be considered old. I just installed Tiny11 on another Dell Optiplex 790 which came out in 2012. With the SSD it starts in 40 seconds and it loads all drivers in the Device Manager, nice!

Thanks for the valuable information . You are right about everything. Also I discover that my current computer cannot be upgraded to Windows 11, so it looks like a new computer, with more RAM is in my future! That will solve a few problems I have been having. Thanks again.