The problem your facing is often caused by a damaged disc. I'll outline two solutions for you, the first involves the disc itself.
1.) insert the disc into the drive, close the autorun screen (setup screen)
2.) click start / my computer
3.) right click the disc drive with your disc in it and click open
4.) hold ctrl and press a or click edit select all
5.) hold ctrl and press c or click edit copy
6.) minimize the window
7.) right click on your desk top and create a new folder, (call it anything you want)
8.) double click on the folder to enter it
9.) hold ctrl and press v or click edit paste
10.) all the fies from the disc will be copied to this folder, if completed without any errors, simply double click on the setup / install icon to install the program.
Method 2 if the above fails.
1.) click on this like http://www.filestube.com/5c66b8541a429ddc03e9,g/PrintmasterPro.html
thats an iso image file of the print master 18 disc
2.) download the file
3.) burn it off to a dvd using ultra iso, a trial version will ,do download it here http://www.ezbsystems.com/ultraiso/download.htm
download it, install it, double click on the printmaster disc, iso file, burn it to a cd
4.) install it as you would but USE THE SERIAL NUMBER AND KEY FROM THE ONE you PURCHASED!. piracy is illegal and fixya does not condone it, but seeing as you already brought it you already have a serial number and key so you dont have to worry. the disc image has a readme file for extra instructions.