no you have lost anything, to install things you need to use dedicated programs, windows by initializing the hd has overwritten the mbr with a pc stile mbr and the ps2 can't read it anymore, and if you even made some partition all is lost, for the mbr maybe by rewriting manually but it's really difficult you can restore it
ps2os betatester, ps2tools codev, hdldump frontend dev
6 sony mc w/ps2os 0.2.4, hdl, ps2rmp1.50,ps2mp3...
na+hd maxtor diamondmax 7200 120GB
PS2 SCPH-30004R V6 ÐM$3 V2 firm 2.4 B.4
PS2 SCPH-50003 V9 ÐM$4 PRO firm toxic os 0.1