The website told me it was too late to replace the power supply. I kind of suspected it ^^
So I'm going to buy a new one on the free market.
I hope it's not too difficult to replace a power supply. I heard that replacing the power supply can cause some BIOS settings to be lost, for example, on AMD EXPO.
Are there any important things to do after replacing the power supply ?
Sorry for this stupid question, but I've never done this before.
There's one incredibly important thing to remember when replacing a power supply:
Do not use cables from the old power supply with the new one, even if the connectors on the power supply look the same (even if it's the same brand). There are many cases where different models from the same manufacturer use the same cable pinouts, but some models have different pinouts and it's better to assume you can't re-use cables from a different power supply and verify otherwise than to just take the risk.
So when you take out the old supply, also remove all power cables that came with it (for the motherboard, the GPU, any SATA devices, RGB/fan hubs, etc.). Looking at your build's parts, that should only be a few cables, so this isn't hard to do, it's just the most important thing that I've seen people damage their parts by ignoring.
Your motherboard should have a CMOS battery that is there just so the motherboard can store the BIOS settings. If it does not retain those settings, that battery on the motherboard is dead and should be replaced. Removing the power supply should have no impact on your PC greater than disconnecting the power cord from the wall (which you should also do before unplugging things in the computer). It's always good to check the BIOS settings when you get a new PC or make any hardware changes though, also just a good idea to familiarize yourself with some of the menus and settings anyway, but that's really up to you. You'll want to have XMP enabled, "game boost" disabled (that's MSI's auto-overclocking and historically it has been not good), and then I'll leave it up to you if you have any interest in PBO2 or other manual overclocking settings. You should also be able to find the "smart fan" settings and set those up for your AIO fans and other case fans. System Integrators have a pretty high tendency to not enable XMP or set up the fan profiles, so it's usually good to set those up in a way that meets your needs (from a cooling per noise ratio perspective).
Edit: I forgot one other reminder that we should probably give as you've said you've never done this before. When installing the new cables, make sure the connectors are all
Fully-seated. This is more critical on the GPU connectors than anywhere else, especially with an RTX 5090, but making sure the connectors are fully inserted is critical (not just when the latch clicks in, which is also required, but when the mating connectors' flat faces are fully touching each-other...no gaps!).
Here's a quick and simple guide on that. It is also good practice to go back and look at all the connectors after you've installed everything and tied down cables to make sure nothing has been pulled on that wiggles the connectors to an angle or something while you added any cable-ties, straps, or zip-ties when doing cable-management.
Edit2: Asking questions is not stupid. It would have been stupid to just assume you know everything or won't have any issues/questions along the way and mess something up because you didn't do any research or were too stubborn to ask for help.
