installed a new OS and everything
OK, bang goes my theory a new OS would fix things. So far it's done the exact opposite. It's made things worse.
Am I correct in thinking the old OS + "bloatware" allowed the CPU to run at full speed?
If so, you might not have installed "everything" you need to permit normal working on the new OS, i.e the correct drivers. Laptops can be tricky because they normally have two power sources, mains and battery. Desktops tend to have only one power source, namely mains. This makes desktop operating systems less complex on the power front.
In most laptops, there are two power profiles which control the CPU's power output, depending on the power source. When running from mains, it's more common to allow the CPU to run at higher or full speed, when programs require more processing power. When running from battery only, the OS will usually switch to another power profile which optionally allows you to reduce maximum CPU power,to extend battery life. Tasks take longer or slow down, but the battery often lasts longer too.
If you don't have all the relevant Windows drivers loaded for the battery and the battery charging circuits, plus any of the laptop manufacturer's software that interfaces with the Windows mains/battery power profiles, you might end up in your situation.
Question.
Have you checked HP's web site and downloaded all the drivers associated with your laptop? Have you applied these drivers? Have you checked the Windows profiles for mains and battery under Power Options? There may be some setting that needs to be tweaked.
If you still have the old SSD and it boots into Windows, you could temporarily re-install it and check all the drivers in Control Panel under Batteries. Make a note of each item and its associated driver and version number. Check the mains and battery power profile settings under Power Options. You'll probably find a few differences which might help you to fix the problem in the new OS.
If the worst comes to the worst, you might consider cloning the old SSD (complete with all that nasty "bloatware") on to the new SSD, and seek alternative ways to get rid of things you don't like. There are online tutorials on how to reduce Windows "footprint" by selectively disabling Services, Registry hacks and other techniques. You may lose some functionality, but you might end up with an OS more to your liking. If the "bloatware" is third party (not Microsoft) it should be easier to get rid of some/most/all of it, with some hard work and a bit of luck.
I recommend getting the new OS working properly, before you attempt to undervolt the CPU again. Windows might have detected something unexpected during installation on the new SSD if the CPU was undervolted and Microsoft made some inappropriate settings based on unusual behaviour, for a CPU with "restricted" settings. I tend to disable XMP, PBO and any other overclock settings in the BIOS of a desktop PC, before installing Windows. Similarly, I restore a laptop's BIOS to stock before installing Windows.
It's not unknown for laptop manufacturers to include trial copies of anti virus software and other unwanted "offerings". Is this the "bloatware" you were trying to get rid of?
