changed hard drives now have error

Hello! I had my old hardrive go bad, so I had a maxtor 120gb harddrive and installed it. I turned it back on. It came up the hp logo, then it went to a screen saying Windows didn't start sucessfully do to a recent hardware or software change. It give me options like safe mode, etc. I'm assuming I did something wrong when I replaced the hard drive, but I don't know what. Please help........ Thanks....Don.......

 

My old hardrive had Xp on it, and the replacement hard drive had Xp on it as well. I have only one hardrive in my comp. as well.

 

Assuming the Maxtor came from another computer and has Windows already installed, you will probably have to do an in place upgrade of Windows. Need more info about your computer.

 

Yes! It was from another comp. with windows already on it. It's an hp 7905, with only one harddrive!

 

do you have any crucial data on it? if not i would recommend formatting it and installing a fresh copy of windows on it.