There’s a few Macs ‘round here (quietly closing the office door so that nobody can count them all) and this 2009 iMac is never powered down - always just put into sleep mode (for many years now). You can check video “card” function using an attached 2nd monitor. Won’t see those lines on it, if card’s still good. Plenty of good, inexpensive, used aluminum Apple 20” Cinema Displays (and other monitors) available on the market. (Normally run a two-display setup here anyway.) BUT if it’s the screen “gone bad” and you don’t have a trusted tech to replace it (or the card) inexpensively… Refurbs (or used Campus cast-offs as mentioned above by 24 Track) are the way to go. All machines here get a yearly compressor nozzle blow-out. Dust is thine enemy. If you do have to retire yours… have some fun and remove your RAM, HD and maybe even the disc drive. Message me and I’ll send you a nice new RocketFish external enclosure for your old HD so you can use it for backup - or simply to retain your old data.