My hand held computer says: Hard Drive (C) being 'repaired'. What's being repaired and how? Thanks.?

It means that when Windows was trying to boot, it was unable to read some of the hard drive.  It compares what is supposed to be on the drive to a table that tells it where every file is.  If there are errors, it needs to fix them.

That may be a simple case of having to update the table to match what is on the drive.  It could mean that it has to repair some of the system files that Windows uses to boot up.  Or it could mean that it needs to find space on the drive and then move some of the files to the new space and block out the old space so it is not reused.

Depending on the type of error, the number of errors, the speed of the computer and the size of the hard drive, it can take from a matter of seconds to several hours.

There has been a data error reading the hard drive
and now the OS is trying to do the following things:
- search the entire hard disk, tiny section by tiny section, for errors
- if it can, copy the data on sections that have errors to sections that do not have errors
- "block" the sections that have errors so that the system will not attempt to put any new data on those sections

It can take quite awhile if you have a slow hard drive
especially if you have a slow, large hard drive.

Your hard disk.

It's probably conking out already. Time to buy a new one. Back up all your files to an external USB drive as soon as possible.

https://en.m.wikipedia.org/wiki/Hard_disk_drive
https://www.techopedia.com/definition/6304/c-drive-c
https://answers.microsoft.com/en-us/windows/forum/all/scanning-and-repairing-drive-message-at-startup-in/462aaed9-7f2b-49bc-8fdb-d62201f3f07a

Your computer and data are about to die.