This may be helpful: https://discussions....105512#15105512
Also, does the Mac make ay noises while the white screen is up? If there are ticking noises it could most definitely be the hard drive. The fact that you said things were slowing down on the Mac would point in that direction. I've lost much of the terminology in my head, but there is a "safe" mode you can start up in. Press the power button. Immediately after
hearing the start tone hold down the shift key. Release the sift key when you see the grey screen. This article may be helpful: http://support.apple.com/kb/TS2570
If it is the hard drive - and if you feel confident in your abilities - you could buy and install one on your own. This wold make your cost much lower - just the cost of a new drive (1 TB drives are going for around $125 or so, but the cost is going up due to weather disruptions were most are manufactured). You have most likely lost everything that is on your current HD unfortunately. You will need your original Apple OS disc(s) to boot from so you can re-install the OS. Then the process of putting all the other software back on the drive follows. OWC is a good source of how-to's for this kind of thing as far as hard drive installs. They are at macsales.com
I've also heard of a process that may allow you to retrieve the data on your bad drive. It requires having another working drive already installed and a way to hook up your damaged drive externally. Here's two articles on the subject: http://geeksaresexy....cover-data.html
Hope this helps you out. (and I definitely hope it is just your HD) Best wishes on this one.