If what you call 'complete format' is a system recovery back to factory conditions (not really clear) your laptop should be as fast as it was when it was new. But I assume you did a lot more than just that (such as installing photoshop, dreamweaver etc).
Did they tell you why they think it's the hard disk? It doesn't seem very likely.
If it works in Safe Mode and not in normal mode, it could be a problem caused by programs/services/malware. A new system recovery back to factory conditions is the solution then. But it could also be an issue of your graphic card; in Safe Mode runs in a very basic way, in normal mode all of it is used.
Any other hardware issue (motherboard or RAM) can lead to hangs also. The only way the hard disk could be the problem is that, for some reason, it doesn't run in DMA mode any more, but in PIO mode. That's easy to check. Then a new disk might be the solution.
The only way to find the cause is by elimination, and even that doesn't always work.
few days ago, I let my computer to download a movie. it took few hours. When I came back and wanted to open the movie, I found my computer in 'hang' state.
Then I pressed power button, shut it down and started again. It again became hang. I thought its because of virus problem and tried to format. Even after multiple tries, I couldnot format it.
Finally, I made only one partition of my hard disk and tried to format again. And it worked. This way I did the complete format of my hard disk. However,my laptop did not worked out the way I wanted. It is too slow. And if I open up heavy programs(having more disk space i.e. photoshop, dreamweaver etc) it becomes hang. I took my laptop to the service center and they said that its the problem of hard disk and I should change my hard disk.
But I dont think that my hard disk is totally corrupted and if it is not why should I change my hard disk? right??
Nowadays, I open it in safe mode.Although, it generates a bit more heat than usual, it works well.
Can you please tell me what exactly is the problem??
And how can I solve it??