You only need to salvage it once, then you have to defend the mothership after your salvage corvette has returned the "support ship black box" to the mothership. Check your objectives.
By the way, Is this your first time playing these games, Zia?
Did you follow the path to it? And you have it installed right? Maybe you need to run it at least once for the registry to appear.
The path is HKEY LOCAL MACHINE -> SOFTWARE -> Wow6432Node->Sierra On-line-> Homeworld
In here you'll see screen height and width. Edit them and remember to select
Decimal to change the resolution numbers correctly.
Here's an screencap of it (sorry about the Danish language in it)