Perhaps you need an upgraded machine.
With that spec the problem is not going to be the PC so what else?
First open one of the sample projects and generate an output from that. Click Open on the RoboHelp Starter page and then click Samples in the ribbon on the left.
If that exhibits the same problem, the most likely cause I can think of is how your virus checking is set up. Our IT once configured every file to be virus checked when accessed even on the local machine. What you describe was the result. They were able to change that and work resumed.
Can you check a project offsite as that would pinpoint / rule out your environment? Rh does allow a second installation but for this purpose you would not need to activate it.
Where is the project installed?
See www.grainge.org for RoboHelp and Authoring tips
OK, here's the story.
Symptoms were as described, however in addition searching function failed in final output.
Probelm found: I had attached several PDF documents by link in a addenda to one of the chapters in the project.
Created a new project and saved/compiled at every step. When I linked those PDFs the whole thing went in the mud.
One troubling lesson I learned was that simply deleting links did not fix the problem on subsequent build. Nor did deleting the PDFs from the project folder help. Had to recompose the entire project to get it scrubbed clean.
Now the project compiles in about 1 minute.