I installed the flip top on my slimline ps2, put in swap magic (CD version) the screen came up, swapped the discs and put the imported game in, then it spins for a few secs and comes up 'not a valid ps2 disc' - any info on why this comes?
I'm not sure, since I have a FAT PS2. Well, perhaps like the other guy said, some ISOs need to be on serperate media; hence why SM comes with two discs. ANY CD-R backups you have, use the Swap Magic CD loader, and any DVD-R backups, use the DVD loader. The error also could be because, you have either tried putting a PAL game on an NTSC system, or vice verca. Please provide more details.
PAL games are European games. The frequency in which they are displayed is different than an NTSC game (American for me). Simply put, you can't just play a PAL all the time, on an NTSC system. You can go get PAL to NTSC converters, SwapMAgic has a PAL option, et cetera.