How reinstall Vista x64 over vista x32


I can't understand why i can't reinstall vista ultimate x64 over vista x32?
I have tried severel times to change disk and so on, but only got ! "error loading operating system"
anyone have the ansver?
Hey! and thanks buddys for the respons here,

I think I maybe must explain more about this problem.
I bought a computer in seconhand and the OS installed was vista ultimate x64 but after few weeks I decide me to format the hardrive (C:smile: and install Vista ultimate x86 RTM without any problem, 2 weeks later i decide me for reinstall Vista ultimate x64 RTM again. because i wanted to use all the memory inside (4gb) and also that i think that OS run littlebit better and stable.

Anyway i have format hard drive and clearing BIOS (RTC) RAM in CMOS (jumper setting) and set bios in default (normal or factory settings). Also set the driver in first run, and harddrive in second and so on. Also try to shift to a other formated HD with same error message when i try booting from install media( error loading operating system) and here I'am:grinning:.

My computer is HP Pavillion.
AMD Athlon 64 x2 Dual Core 2600mhz (5000+)

Sorry for my English.

Mike from Sweden


The point of error!
when i restart computer and press Esc tab to tell HP to be sure that computer start with CD/DVD after 2 sec the screen is black and then comes the message " error loading operating system" I have try this procedur several times with same answer.
But if i put in other disk (OS) e.g XP x86 with sata drivers, I see other result "press any tab to start CD/DVD" and the install I'll continue ?

Mike from Sweden
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Sounds as if the PC is not finding the 64 Bit disc. Where did you get the media for the 64 Bit version?
No! unforunately I can not find any AHCI options. strange all this because i change to vista x86. before i did the format and so on I use the media disc ( vista ultimate x64) when i try to format from disc everything run ok, but i not change aything that time. Maybe have to give up soon, and install xp and upgrade to vista x86:huh:
Yes i do so! that are maybe something wrong with the drivers i think. Taking my hat of
and thanks for all respons.

I will return if I find any solution of this issue.
Regards Mike..