yeah winXP is so old you can't even GPU mine from it. win7 or 8.1 still work good, but effort is needed in those systems to remove M$ spyware recently introduced as updates, Win10 so useless... so yep Mac or Linux is the best choice, i'd highly reccomend Linuxmint for a beginner (you can install it to dual-boot on your windows machine, just be careful not to erase windows...)
https://linuxmint.com
Cybercriminals are now targetting Macs too. I would store mine on an iPhone but if you lose your phone you are screwed. Best storage option is still hardware wallets.