Critical Error! Cannot locate hard drive...Private data at risk etc. Checked hard drive. 50 % left. Ran SuperAntiSpyware 2 times until clean. Ran Malware. Found zero threats. Ran Standard Defragerations, found and got rid of one threat out of six. They want me to buy the Advanced Defrag for $65.? to kill the other 5 threats?

When a hard drive has bad read/write sectors it means the magnetic oxide layer on the disc platters are failing. Before you made an image of the hard drive you should have ran Error Check on the C Drive. This checks and locates the bad sectors and moves the data to an undamaged part of the disc platters and then locks out that bad sector so data cannot be written on the bad sector.
I recommend you do a fresh Windows install on your new hard drive to fix this problem and install the laptop's device drivers plus your programs and data.

your computer cannot boot from the hard drive or cannot read the drive.the drive may be corrupted so zero-fill it.and if you think that your hard disk is in healthy condition then you can try one by changing your battery and observing the screen by pluging the laptop to the wall socket and also unplugging.do you see any difference? if yes then problem with the battery(if seen that the laptop reboots after being plugged).to the best of my knowlege,the hard drive is corrupted.

As I understand it, SMART is correct 50-60% of the time...means it's wrong 40-50% of the time.But..You can't take the risk, you have to assume something is wrong with your hard drive. So, i f you have important data there, go to a repair shop and they can save data from your hard drive and replace it, if necessary. If you want to solve it on our own, you need a boot cd with error checking. Any live boot cd with linux does that. Also, there are several live boot cds like Hiren's Boot, with rescue options.

sounds like it is over loaded with running apps some of these could be spyware try using Spybot search and destroy to remove these http://download.cnet.com/Spybot-Search-amp-Destroy/3000-8022_4-10122137.html?tag=mncol;1

I guess you are using it thru USB...
This is a general issue with all external devices connected thru USB, many times the USB reacts to an external device as though they dont exist.

The best solution is to shutdown the PC remove the device from the external USB port clean the connection, the USB cable connector, USB port etc and reconnect.

This situation could also happen if you have dropped the device, any little shake/**** could make changes to the internal system of the disk.

Try using a different USB cable to connect it to the PC

My personal experience is..... USB devices should be used sparingly and for things that are not critical like (MP3, mobile, camera etc) I rarely use external harddrive thru USB, never to store critical data.....an issue ever with the disk the data is almost gone unless it's recovered by an hardware expert after opening the drive and thru special system/data recovery devices.
The last option is to format it again, many times my MP3 player has been funny and gave me similar read issue and I had to format it many times to be read again by the PC, so i learnt a leason from that......never to connect a harddisk from USB, it's better to have larger harddisk inside the PC and use some DVD disks to carry your critical data to the place of work....(they cost less also) if they fail just throw them and use a new DVD disk

Try deleting all files within the following locations: (In Windows Explorer (not Internet Explorer) click "Tools" and select "Folder Options" then choose "Show hidden files" and take the tick out of "Hide protected system files")

%UserProfile%\Local Settings\Temporary Internet Files\
%UserProfile%\Local Settings\Temp

This is the action of some form of malware, masquerading as Windows Security Center. It roots itself in the current user's temporary data folders and as far as I know, doesn't affect all users.
It is also a hidden process but as far as I know, doesn't execute any particularly malicious code, just a really annoying notification (which you'll notice changes).

Your best bet is to reimage the machine. Even if you get rid of the virus you also get rid of the file(s) it infected. That means those files are no longer available to run and they typically are critical system files. Viruses will hide and then repopulate if you don't completely format and put a clean image on the system. Because you probably don't want to loose all of your data you will want to back it up. Here is another problem because some of that data could be infected as well. I recommend removing the hard drive and use another computer that has a good anti-virus system, backing up your data to another device. Be sure to check your email files because they can bring a virus into your system. Chasing a virus can be frustrating and ultimately unsuccessful. Bite the bullet and give yourself a clean system.

A "critical error" could be caused by many things: Faulty RAM, a bad cable, overheating, faulty power supply, corrupted hard drive, damaged circuit trace on motherboard, and others. To fix, try removing the hard drive and trying a known-good unit, if possible. Format and do a clean system install on the replacement drive. This way you may be able to salvage data from the old drive once you get the system back online. Also make sure all RAM and any expansion cards in the system are fully seated. If this process doesn't help, you are probably dealing with a faulty cable or bad RAM. In my experience, the possible culprits are as follows, starting with the most likely:
1.Faulty/corrupted hard drive 2.Faulty drive cable 3.Bad RAM 4.Faulty power supply (can cause drive corruption) 5.Bad motherboard 6.Incorrectly seated/faulty peripheral cards 7.Bad CPU
If you can describe the circumstances surrounding this failure, or if any upgrades or other service were performed recently, these will be clues as to the source of the error. Please post them if available.

The drive is likely failing; Windows is unable to located a boot record for the drive and therefore it wants to format it in order to continue; trying it on a 2nd pc confirms this.
It may be possible to use a utility such as Data Doctor's Data Recovery to recover the data but it's going to cost some $$.
You can check out the utility at http://www.software.com/view/8432/0/data-doctor-windows-data-recovery-software
I've used this in the past to recover data from drives that were overwritten; and to undelete files that were lost when someone accidently deleted a user's windows profile.
Hope this helps! good luck!

use a data recovery software ! u'll most probably be able to recup. u're files (most of them)(it will take a LOT of time) and even fix the drive problems (logical or fizical )