My PC won't accept Twain 5 for my flatbed scanner, what am I doing wrong?!?

I have Windows 98, and an Epson Perfection 610 flatbed scanner. I downloaded Twain 5 from the Epson website, and tried to install it with InstallShield Wizard. Tells me to restart computer. I sign in. It says found new hardware. Tells me to insert Windows 98 2nd edition. Tells me that the file 'ubscan,sys' on CD Rom cannot be found. I re-insert CD Rom. try to copy files from D:\win 98. Tells me to insert disk again. Go to skip files. Tells me to restart computer. Etc. etc. What am I doing wrong? PLEASE help, because when I then go into Microsoft photo editor, it tells me that Twain 5 is not found.