I have created a new blank project in the RoboHelp 2017, and i kept the name as "demo1" on my desktop path"C:\Users\gangadharb\Desktop\New Project". But it is showing as the project or path contains illigal charecters. I also not not able to insert images in the new topic. Please help me regarding that.
Try creating it in Documents>My RoboHelp Projects. If you get the same issue there, then try without an spaces, use underscores. Spaces are not illegal but worth a try.
I can second the use of underscores over spaces.
I once had trouble adding a logo image to a responsive HTML output. No matter what I did, change the resolution, change the file type (svg, png, jpg), nothing worked. The file would just not appear. While the original logo from the sample file worked fine. Even Adobe support couldn't figure out what was wrong.
Then I noticed that the file that was working had only a single word for a filename (something like logo.png). So I added underscores to my own logo file, and lived happily ever after.
No error messages that I was using illegal characters when I selected the logo file with spaces, but it didn't work anyway. So if anything strange happens, replacing spaces with underscores in your filenames or folders is the first thing I'd look at.