win 98

hey i already downloaded dos 7.1 and installed then i installed win98. A message appeared that i cant use win xp. I ignored it. after instalation , when i booted my pc, my intial c: drive where winxp was installed was missing (initial drives were C\system(winxp) ,win 98(name) F:\ games). After dos and 98 installation, my d drive became c:\ drive and myF:\ drive became d:\ drive. ilost all the data of about 5.6 gb in the initial c drive and the drive doesnot even appear in My Computer window. i want my old c:\ drive back as its capacity is about 10 gb. i also want to reinstall win xp. What should i do? should i try to use partion magic? thanks 4 ur concerne...