Computer Hope

I want to be able to take my PC to a shop if I need them to fix something.  But they always want you to leave it there with them, and I do not like that because they could look through your personal files. 

So I am wondering if there is a way around this issue.  Like perhaps installing two harddrives and the OS would be on one and your personal files on the other.  I've heard you can do that, but not sure how.  Anyway, would that solve the issue, because if you need to take your PC to the shop to get something fixed, you could just pull out the harddrive with your personal files on it.  Would that work, or not?  Because I'm not sure if it will work right if you have that harddrive taken out if it is set up to save your files to it. 

And if it would work, does having two harddrives working together like that, slow your computer down any? 

I have two SSD harddrives on my computer. Using one hard drive for you personal files would be a good solution. You could also use an external hard drive for personal stuff; much easier to disconnect and re-connect.

If you had to take the computer to the shop to get worked on, would it still work fine that way if you take out the SSD with your personal files on it? 

Where do you get a computer with two HDs anyway?  Can you buy them like that?

I would use windows bit locker to secure your profile and have a profile you don't use for the tech to use.

Here is how you setup bitlocker                      https://support.microsoft.com/en-us/windows/turn-on-device-encryption-0c453637-bc88-5f74-5105-741561aae838

Bit locker is not available in Home editions of windows.

If you do use Bitlocker there is the option to backup the key to your Microsoft account to a flash drive or to print it out.

Don't loose this key as if there is a problem with your profile no one can get access.

Aside from protecting your data from someone who is repairing your devices, it's a great idea to keep your personal data on a separate hard drive or other recommended online location as well.
I've learned this from a guy who's mission is to protect the personal privacy of regular users, who's experience and solutions I completely endorse.
In case you're bothering to do a backup like this, you might as well use the experience of someone concerned with personal privacy. Here's a list from Rob Braxman's YouTube site search on this subject... 
https://www.youtube.com/@robbraxmantech/search?query=backup

I like Lisa's offered solution to encrypt the data and have a separate profile specific for the tech guy to use to check on things without privilege to seeing the encrypted data.

And just to make sure you don't lose your data, be sure all important data is backed up somewhere else than this computer because I have seen some tech guys wipe clean a build and say problem solved before and customers lose their data because the tech guy didn't backup the personal data nor ask the customer for the ok to wipe it clean and clean build it.

I've had to help people before who had their data wiped out by a tech guy and as long as the sectors not overwritten where the data was located I have tools to recover deleted data and got partial data recovered for them.