I am in the same boat, for the second time in a few months.
I was convinvced the first time it was some kind of Malware issue but it turned out to be a hard drive problem. In Windows XP and older, it was always obvious when the hard drive was acting up, but on my Sandy Bridge system with a used re-formatted 500G wester digital green drive, after 2 months it just got slower and slower to the point almost every window would come up as not responding for a while as I try to get anything done. The funny part is that the CPU usage was never high, the drive did not get noisey, and if you were seriously patient, it would eventually do what you asked. But what would normally have taken seconds was more like 10 to 20 minutes. Some programs would error out, the the OS in Win 7 will just kep trying until it gets the data from the drive. Back when my first system did this, I replaced the green drive with a Seagate Barracuda 7200.12 and that computer has been super fast and responsive ever since.
Now I buile a second Sandy Bridge machine for my wife. I used the newer Z68 motherboard and started day one with a brand new Seagate Barracuda 7200 ST3 with the new 32 meg cache and excellent ratings on the web. For about a month, this thing was blazing fast, no lag ever. Then within a cpl days it went from my wife saying it hung a few times to being unable to make it to the log in screen in under an hour. The drive has only 124G of data on a 1T drive and has been in use just 1 month. It has a 5 year limited warranty. I tried to do all the usual checks, but the computer became so slow and unstable I could not even run a disk check on it without it erroring out. I loaded up a bootable USB stick of Linux and all the hardware checks out just fine, Running in the live boot linux we copied all of our data to a USB drive from the dying drive with no issues. It appears the failing area is in the OS and the data is fine. Of course that great 5 year warranty means they will send me a new blank drive once they get my dead drive, so I would be out all my data and PC for a few days at best. I went ahead and bought another drive, and re-loaded windows from scratch, and as expected, the computer is running perfectly again. We did backup all the data, but for "fun" I dropped the dying drive into a BLACX eSATA dock and was able to pull all of our files back to the new drive without a single glitch. Though I did fresh re-install all the software and drivers, only pulling content. All of our music, movies, home video, and of course a huge pile of documents.
Every search I have done on the web keep pointing to software erros when you complain about a slow PC. I think we need to find a better test to determine when a drive is failing like this. I also think the new high areal density drives are far more likely to have an early failure. Each bit is just getting so small on the platter surface. My plan for now is to just make sure and do a full virus/malware scan on the dying drive in the dock. If this drive was not so new, I might do what I did with the WD Green drive. I just did a full low level format, not a quick format, and it did find a group of bad sectors and just mapped them out. I have been using it as a test drive for new PC builds and it has been stable so far. Another suggestiong I got was to partition it to not use the first few gig or so as that part takes the most use every time the system boots or does any OS operations.
I would be very interested to hear what other people have run into on very slow Windows 7 desktop issues.
Edited by hamluis, 24 January 2012 - 01:30 PM.
Split, PM sent new OP.