I have a laptop that I just had to replace the hard drive in. I did a fresh install of Win7, and it worked fine for a week, but now it's running very slowly.
I installed Microsoft Security Essentials and Superantispyware when I did the fresh install, and neither of them found anything(even in Safe Mode). It runs slow in Safe Mode as well as regular. It can take 2-minutes from clicking an icon until the time it opens(IE8, Firefox, Start menu, etc. doesn't seem to matter).
I removed the HDD, put it in an enclosure, and I could access all the files/folders quickly when plugged into another PC. So I'm beginning to think it's the CPU(vs. the motherboard, as everything seems to work - eventually). Sound plausible?
The problem is its a Compaq CQ62, and while I can find motherboards online, none have the CPU. It's an AMD Vision, but I really don't know the specs to order just a CPU.
Any thoughts before I throw any more $$$ at this?
CPU's are typically built into the main boards on those systems.
How much ram are you running?
What services are enabled?
What processes are running in Task Manager?
I checked & the CPU doesn't come with the board. After the problem started I did another fresh install of Win7, but it still is super slow, so I'm sure it's hardware.
I'd just like to narrow it down between the motherboard & CPU. 
Since you made no changes to the motherboard or CPU, I don't see why either of them would suddenly crawl to a snails pace.
More I would be inclined to suspect a problem with the component you did replace, namely the harddrive. In particular, the speed at which it's transferring data.
No expert on this subject am I. But I have replaced a hard drive or two, and had trouble with compatabilities, as well as how I set the drives up, and getting various dip switches correct.
This still says "software" to me. Whether that is Windows or a program that is on your hard drive uninvited, I'm not sure.
I'd be checking for programs/other processes in Task Manager that are hogging CPU or RAM. I would also run a scan using MalwareBytes - IME, the best anti-malware program out there. And although I'm not certain it will help, run a hard drive defrag on it just in case. When this has happened to me, the culprit has usually been a piece of software pegging the CPU load.
Anti-virus software is a virus. Check the settings and stop it from checking every exe every time they load from disk and stop it from checking every byte you stream from the web. Set it to scan overnight and leave you alone the rest of the time.
Win7 is already a pretty big hog but if it is busy building indexes of all your files for fast searching... it is painful. Again, set this to happen when you are not around or turn it off.
Add RAM.
A quick update: I dug through my pile and found a drive from another laptop that died a while back. Installed it and Win7 again, and everything seems to be working fine now.
I'm going to put the "new" drive in an enclosure, format it & see how it works.
Thanks again for the help!
When looking at hard drives, pay attention to the spindle speed and the amount of cache. More is usually better :)
