Do i need a new hardrive or just a new operating system?

I have a Toshiba Satellite A300 which is about 18 months old. Problems started when i got error messages constantly popping up telling me i had corrupt files and to run chkdsk utility. I was unable to run a chkdsk utililty nor was i able to do a system restore. I sent it to a friend for repair who said my problems were because i had vista and i now have bad sectors on my hardrive because of it. He told me to consider downgrading to XP. Within a few month the corrupt files messages came back. With windows 7 recenbtly being released i asked my engineer what he thought of it. He told me it was meant to be good and anything was going to be better than vista. I bought windows 7 and passed it on to him to install it.It was not a complete new install as it was only an update version that i had bought. I've had my laptop back for a couple of days but it is much worse. I love the look of windows 7 yet sometimes it turns itself off and some times it doesn't recognise the built in mouse or keyboard. It also sometimes starts up with a different screen resolution. After speaking to the engineer again he told me my problems are now because of windows 7 and also because i have a toshiba. He has now told me i need to get a new harddrive and go back to vista or XP. I am completely confused and do not trust anything this man tells me. A technician from my uni has since told me it doesn't sound like i need a new harddrive and suggested just doing a full recovery to take it back to new.