Obsolete Files?

[Johnny]

In the computer's hard drive I have a folder for Premiere Elements 7 projects. (I had PRE 7 before getting PRE 10.) That folder takes up 100 GB of space on the hard drive. When I try to open a file from the folder, Premiere Elements gives the following message:

File Import Failure
Error Message
This type of file is not supported, or the required codec is not installed.

I have the files saved in the external hard drive as well. When I try to open either of the files that are in the external hard drive, they open in Premiere Elements (as completed projects).

Do I still need the files in the computer's hard drive in order to access the projects in the future, or is just having them in the external hard drive enough?

Hoping to free up space on the PC since its hard drive has just about 50 GB free.

[Steve Grisetti]

Johnny, please don't ask the same question in two different posts. It's very confusing.

[Johnny]

Sorry about that, Steve.

As I was posting my question initially (in the "Credits" section), it occurred to me that I also was asking advice about whether or not I need to keep the files in my computer's internal hard drive, so I thought I should post that question here. I think because I'm not entirely clear on some of the terminology, I'm unable to understand whether or not I need to keep some of the things that I have stored on my PC's internal hard drive. I just don't know whether it's okay for me to delete those PRE 7 files and free up 100 GB there (whether doing so will prevent me later from accessing the movies that I had put together a while back).

Anyway, that's what I'm trying to learn about. There's just a lot to absorb, and I don't want to lose things to which I had devoted a lot of time.