|Okay - before you rush out and buy Win 7, the disk may have physical/mechanical errors that the Windows error checker cannot detect. For that you need the drive manufacturer's own drive diagnostic utility, so you'll need to find out what make it is. These testing utilities are free for all makes of drive.|
I advise you do that as the next step, because if the drive is failing, throwing another operating system at it isn't going to fix it. If you post the make of disk I'll reply with a link to the utility you need for it. Oh, and those drive diagnostic utilties all run from a bootable floppy or CD so it doesn't matter how messed up Windows is - they will still run.
Bottom line is, don't spend money on Win 7 in the hope of fixing your problems until you're sure the disk is in good health physically.
Furthermore, if your disk does pass okay and you do decide to get Win 7, you need to be sure that all your current software is compatible with it, and that you can get Windows 7 drivers from your PC manufacturer's website. The Windows 7 CD has many drivers on it which will be installed during installation if setup detects a matching device connected to your PC, but be prepared for some missing drivers - Win 7 doesn't have them all.
Microsoft has put up a website to help those upgrading to Win 7:
Windows 7 Compatibility Centre