Differential diagnosis on no post/beeps/vga

[luminous]

Grrr since i made my new custom pc from here i thought i`d get shot of the old one locally.I took the hard drive out and used it in my new one to test out different configs with oblivion.So today a buyer calls want to see later.
Early today i put hd back in to reformat,install and here we go no post/beeps/monitor signal,isn`t that just typical? its been working fine..
Anyway,i reckon its 2 1/2 yr old but specs are

Athlonxp 2600 barton core
Gigabyte 7vaxp
Radeon 9200 agp
80 gig wd drive
Standard cdrom
Newish 400w mercury psu/case (yes i now know never to use cheap psus but it works lol,hiper is in new one)

So far:
All fans are spinning (including hd)
Tried diff agp/pci gfx card
Swapped in good mem
Diff hd/jumpers
Checked all cables/put in new ones
Will now try a bios reset(its odd on this board btw,battery out 30 mins/short pins) and spare psu.
Oh just noticed barely audible `click` sound i think from onboard speaker(like its trying to beep but can`t?),or could it be voltage on board somewhere?.
What are the odds the mobo goes day i get to sell it,just my luck..
Out of box thinking encouraged

 

[xirokx]

no post/beeps/monitor signal,

Swapped in good mem

I would say its the mobo.....you have already tried resetting CMOS and all other things...

sorry mate....but i hope its not for your sake...

 

[luminous]

Spare psu didn`t work either,looks like mobo.What are the odds it happens on day i might sell it .Not sure if its worth picking up an a socket mobo,heard they`re thin on ground now.

 

[luminous]

Took mobo out of case as final troubleshoot and still no dice.
Last month i`d cleaned out cpu/fan/repasted so as last chance motel goes did it again and now i get to post and all beepy ,hope the rebuild goes alright now.
Maybe i hadn`t seated cpu correctly hmm.
I used the silver paste stuff i used with a64,is that ok with athlon xp?