You can attempt the recovery of bad sectors through Windows built-in tool. Go to My Computer, right-click on the disk where bad sectors are appearing, then click on Properties. Click on the Tools tab, and select the error checking tool. When that starts, make sure either "Thorough" or "Scan for and Attempt Recovery of Bad Sectors" is checked. Wait a while, possible a long while.
In the meantime, you should start backing up crucial data more regularly. Bad sectors are usually a sign that your hard disk is on its way to giving up the ghost.
1. Backup your hard drive ASAP. As r_manic said it can "kick the bucket" any minute.
2. You can download the free mhdd software tool from http://hddguru.com/content/en/software/2005.10.02-MHDD/
If there aren't too many bad sectors this tool will attempt to repair the drive.
Even if the disk is useable never store critical data on this hdd
hdd rule #1 - NEVER rely on any single data storage device
second, all hdd's have bad sectors - thats why they have spares! it wont "kick the bucket" but you can risk data corruption, hdd death will only occur with mechanical or electrical faults etc, so nothing too serious.
Run a tool to gather S.M.A.R.T. information off any hdd and more then likely you will have a "sector reallocation count" more then 0 meaning YOU HAVE BAD SECTORS and they are safely disabled and reallocated etc - nothing to worry about
as for repairing, get "seatools" or "western digital data life diagnostics" (both available and will repair bad sectors for your hdd) and run a test and get it to fully scan the hdd (surface scan), which will find and replace any bad sectors and check the overall health, and also within windows *after* that run, run chkdsk /r to recheck all your data etc