I've recently built a gaming computer with help from a friend. I saved me a few bucks by going with the option of not buying a new HDD.
However, I've read that if I try to install the old HDD (1TB) to the new computer, some problems might be caused.
I can just download everything again, I'd prefer a nice new built with no problems. So, how could I do that? Would I need to erase everything on the HDD before installing it? some kind of reboot?
Ty in advance! Have a nice day.
Moving an OS drive to a new system doesn't always go well as the OS will contain the drivers for the old motherboard and hardware. These usually fail on the new/different hardware.
Backup any files you want from the drive. During the windows installation you are given the oppurtunity to delete/create new partitions. Delete all partitions (this destroys data) and create a new one for windows to be installed to. Proceed with the windows installation.
If possible try to download all the drivers for the new hardware before starting and put them on a flash drive or something. This will help save time once the OS is installed.
IMHO, you tried to save money in the wrong place. If your old computer is old enough to need replacing so is your old HDD. They don't last forever and they often fail without warning. You will also probably need a new OS as your old one is probably an OEM version meaning it is tied forever to the original MB. If I were you I would get a new HDD or SSD and install your new OS. After the new OS is running OK install the old HDD as a second drive and migrate data ASAP to avoid failure.
If you intend to boot off of it, the hard drive must be purged of all Windows files. If you remove your Windows files, any programs on it, including your games, won't work anymore even if you reinstall Windows. If you have the option, back up all your files to online storage or a separate drive, then wipe the drive. Whatever you do, *do not boot it before wiping it* (waving arms frantically) - it will invalidate your Windows key.
However, ram1009 has a good point. If your old PC was in need of replacement, so is your HDD. You might consider replacing it.