failure to startup

Are there any error messages or does it freeze at the Acer screen?

If there are any floppy disks or CD's in their respective drives, eject them first.

If you press f12 and go to boot menu, and choose Hard Disk, does anything happen?

you can try another keyboard - it can be bad
other than that, i would remove all deviices, and start with the minimum, till i can enter the bios :
mobo + cpu + 1 ram stick, video card, PS, keyboard and mouse

no error messages,but freezes at Acer screen
no floppy disk drive fitted
no cd in drive
pressing  Del to Enter SetUp  or F12 to enter Boot setup has no effect
since sreen appears to have frozen
os is vista home premium 9 months old

why am i getting identical possible solutions from
2 different experts?
as i said aqcer screen appears to have frozen so pressing DEL or F12
has no effect

what is identical ?

identicall means t6he same in all respects
getting identical avice from  nobus  and callmecheez

CIC  means christ i'm confused

Is it a new machine(under 9 months) ?
Does the Hard Drive light stay on?

Do you have any other external devices plugged in?

I wouldn't say our advice was at all identical, but whatever!

hd light comes on for about 10 secs and goes out
nothing attached except modem

no offence meant. looking at ms HELP ,it appears that there may be a repair and recovery cd but it may me loaded on hdd which at the moment means it cannot be accessed

Try without the modem.
do you have laptop or desktop?

9 month old desktop

unplugged modem,no difference

i see nothing identical... please clarify

what we can try is opening the desktop and shorting the CMOS.
this is done by locating the battery on the motherboard and removing it(with power unplugged) for about 15 min.
http://www.computerhope.com/issues/ch000239.htm

When done correctly it will Reset the system CMOS or Bios to its default values.

If that doesn't help you should consider sending it back for warranty.

STOP!
For many manufacturers, including Acer as far as I know, opening the case will void the warranty.
If it is a hardware problem and the pc is less than 12 months old, it should be returned under warranty for either repair or replacement.

downloaded MS  Vista Repair disk,which is not supplied by many OEM vendors,and this disk fixed the problem

phototropic,you are correct in that such action invalidates warranty,so therefore i located as above  the repair disk and we are up and running again

Glad to hear that you got it sorted.
What was the download you used?

http://neosmart.net/windows-vista-recovery-disk-download/

it is an iso file but full instructions of how to burn to disk are given in artcle
i used vista X64

many thanks everybody concerned

how did you boot off it if you couldn't even get passed the boot screen?