I'd try a new hard drive. This may confuse some but if the drive is taking longer to get going, this could happen. Seems like a cheap fix.
when booting up my laptop fails to detect the hd, gives the following error message , no bootable drive.
if i restart it then finds the drive and boots up normaly, scanned for virus's and adware came back clean. also disk was scan for bad sectors and no problems were found.
running windows vista