It has been some months that my PC (ASUS P5K-E, Intel quad-core processor, 4GB RAM, 4 hard disks) sometimes hangs when it has to read and/or write to disk. This is really apparent when for example I'm playing, and everything goes fine until it has to load something from the hard drive - it completely freezes for 1-1.5 secs. It's not a natural slowdown, it's a pathological hangup (mouse pointer freezes).
That was just the first symptom of a greater problem.
Two days ago I had a blue screen of death (I didn't manage to read what it reported, I've just seen it was something related to a "BAD POOL") after which Windows 7 didn't boot again. There are no bad sectors on the disk, but the NTFS file system is a total disaster and hundreds of files have disappeared or become unreadable.
Is this a symptom of bad hard disks? I don't think so. In my PC I've got 4 hard disks (on a SATA2 bus): on the first I've installed Windows 7, on the second Windows XP, on the third I've put some programs, on the fourth all the data (documents, etc...).
The freezes are happening on both Windows 7 and XP whenever I interact with any of the hard disks.
The S.M.A.R.T. status for a disk indicates some bad sectors, but it's the third disk - the one that's less important and not used so often.
The PC is directly connected to the power line, without UPS. However I don't live in a place where surges are frequent and "important", and I didn't notice any in the last few months. The PC is not affected by other problems, like random reboots or shutdowns. The RAM is good (passed Memtest86+).
The power supply unit is two years old (like the PC), and it not used to be a cheap/crappy one. I don't know about the quality of the the SATA cables, however they seems new and undamaged. The machine just seems fine: it's clean and it's not overheated. It used to work fine since some months ago, when it started messing with the disk I/O.
Where/what should I start from? Should I buy new SATA cables? Should I buy a new power supply unit? How can I know if the motherboard itself is damaged? What tests can I perform?