The product key will be in the system but because it is encrypted, it will be unreadable.
On an OEM machine, that key will be a generic one and wouldn't reactivate the volume if you performed a clean install.
Machines that came with the OS pre-installed usually have a recovery partition which you can use to factory reset the machine back to how it was out of the box.
However, because this will wipe all of your personal stuff and any programs you may have installed, you will need to back up your personal stuff to load it back in and reinstall any programs after the reset.
This article may be of interest for how to repair an emachine but I'm not familiar with Easy Recovery Essentials so couldn't advise creating a boot disk for it.
https://neosmart.net/wiki/emachines-recovery-disk/I always set my laptops to check the DVD drive before the HDD in the boot order so that if I have any problems, I can stick an install disk into the DVD drawer and then switch the machine on where it will boot up from it.
You can open a disk drawer without turning the machine on by waggling a suitably sized darning needle or straightened paperclip into the small hole that is in the disk drawer and that will pop it open.
To change the boot order you will need to tap the key you see when the machine first boots up for Setup.
It's usually F2 and then use the cursor keys to navigate to Boot then use the cursor keys to select the DVD drive and use F5 or F6 to move it to the top - ensuring you select Save and Exit to make the setting permanent.
If the machine doesn't boot then you may also be able to tap F12 as you switch on to give you a one off boot order change.
I would go ahead and download that Vista x32 bit ISO and create a bootable disk as with one of those you can boot the machine up with it and navigate to the recovery environment to select the Command Prompt and enter these cmds.
First you need to know where the computer sees the volume as it doesn't always see it in C:
Enter bcdedit |find "osdevice"
That is a Pipe symbol before find and is the uppercase of \
Using the partition letter that gives you, use that instead of the X I use in this cmd -
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
There is a space before each / and that will compare your system files to those on the install disk and repair as necessary.
From within Windows you can run a Command Prompt as an admin by going Start - type cmd - riight click on cmd and select Run as administrator - accept the UAC and enter sfc /scannow
If that reports it is unable to repair some files then you would run the offboot sfc /scannow.
There is also the cmd chkdsk which is either run as chkdsk /f or chkdsk /r
The /f switch will repair any files and the structure of the HDD whereas a /r switch will check the physical side of the HDD to look for bad sectors and has the attributes of /f.
If a chkdsk /r reports any KBs in bad sectors then it's time to create a full system image of your computer in preparation of the HDD failing completely.
Some OEM machines can be repair installed where you have serious OS corruption, but you would need the COA sticker key that is usually on the underside of a laptop and somewhere on the casing of a desktop PC as it needs to be reactivated after the install is complete.
However, as machines age, that sticker key becomes unreadable.
I've made a note of mine on Win 7 laptops should I need that key and mine have faded.
Two are obsolete now as I've upgraded them to Win 10 and have just one laptop remaining with Win 7.
A repair install is better than a clean install as it doesn't affect your personal stuff or installed programs, but it would need all of the Windows Updates reinstalling.
I hope this novel will be of some help should you need to repair your machine - there is of course, the Windows Repair program you can download from
www.tweaking.com
