And would each computer (or drive) have it's own table or - everything goes into one (huge) table?
One big table. A good rule of thumb is that tables (and fields for that matter) should be named so generically that someone without knowledge of the system knows what each table/field is for. Also, you shouldn't use suffixes, prefixes or numbers in names. So that means you would never have a table/field named after a specific computer or drive, or have tables/fields like [Computer_1], [Computer_2]...etc. Generic names should rule the day.
Jine don't I want to Join tables? Isn.t that what makes a relatioanal db?
Yes, but in the right manner. Almost all JOINs should be on numeric fields--the autonumber primary ID of one table (parent) goes into the other table (child) and that is how they are joined, not by text like you had done.
If just SELECT * FROM Drives WHERE [Drive Letter]="C:"; doesn't that restrict it to one Drive/Computer with no need for a Computers table?
Technically no, it only restricts it to one Drive (C

Now here's where it gets tricky and goes back to the storing the ID instead of the ComputerName in Drives. If you do not have a Computers table, then you just store the ComputerName in Drives. If you want a Computers table then you remove ComputerName from drives and store just the ID from the Computers table and JOIN them when you need the Computer Name from Computers and all the Drive information. But like I said, I don't see a need for a Computers table because you only have 1 field of data in it. But also again, you are building this piecemeal so maybe in a few hours you will relaize you need more information in the Computers table and that will necessitate one.