I was having the same problem with MSN Messenger 7.5 on XP, which before worked despite having to try to login after 3 times or more, until it stopped for good with error 80048820.
I solved the problem with the help of a friend, who gave me the hint to open a registry file by enabling POSReady 2009 and then installing the windowsxp-kb4019276-x86-embedded update file and then restarting Windows. After that, MSN 7.5 came on the first time! It works for Messenger 8.1 and 2009, but you also need to enable TSL 1.2 in the registry and that’s it, you don’t even need to use the proxy.
PS.: There are two files and I will leave them here. XP needs to be up to date or at least have the latest updates.
PosReady.zip (264,Bytes)
PT-BR windowsxp-kb4019276-x86-embedded-ptb_422a86a219d378e980cf8aa821df8a80bb810055.exe (1,1,MB)
EN
windowsxp-kb4019276-x86-embedded-enu_3822fc1692076429a7dc051b00213d5e1240ce3d.exe (1,1,MB)