Partmgr.sys error 10 easy points(to whoever answers and helps me correctly)?

Whenever I turn on my computer it says boot disk error insert system disk and I do then I run it and it loads up then I get the bsod(blue screen of death) and it says error can't contue yada yada needs partmgr.sys file. So where fan I get that file? Whatfolder do I put it in? And why does it sometimes turn on with the windows xp cd inside and sometimes not? It's really pissing me off. If I just download that file then I'll put it in a flash drive run a live Linux cd and put it where it needs to be. Also if it has something to do with the system settings then idk. I haven't changed anything,put more or take out RAM everything is just how it was b4. Also sometimes when the cd goes through it says drive not detected and it's connected right I even checked.