cant convert my win xp pro from fat32 to nfts

Hi, recently my kids did something with the family pc and we could not use it anymore, so like it has been more than a year that we did not do a repair or fresh instalation of win xp I decided that it was about time.

I started with the the repair but I could not,so I tried the fresh instalation but I could not install win xp anymore, it said that it can not format my drive, i also I used a utility from the hard drive vendor (seagate) to help me with the instalation, but still I could not, I also use another utility from the vendor to fix errors but find none. All this was something that I have done in the past without problems.
So a friend took the pc and he was able to install win xp but in fat32, he divided the drive in 2 partitions, one for widows and the other for anything, since then we have tried to convert it to to nfts but not luck.
Any ideas about the problem and what can I do?
How can I convert it to nfts?.

 

http://support.microsoft.com/default.aspx?scid=kb;en-us;307881