I am not so sure which Version of Microsoft windows operating system is installed on your computer, but I would assume myself as Windows Vista, since this is a known issue with Windows Vista, (if my assumption is wrong, let me know so that I can help you better).
This happens when .man (.manifest) file in the windows is corrupted or infected by virus. In most cases, after installing multiple antiviruses on a system or after a virus scan.
First of, you need to try with the windows vista recovery disk. I hope you still have one or if you don't have one, download the Windows Vista Recovery ISO from here (click here)
[let me know if you have problem]. After the download is completed, burn it on a dvd. If you would burn the DVD or the CD on a Windows Vista or win 7 system, simply right click the ISO file and select "Burn Disc Image" or etc... That'll create the bootable disk automatically, or if you are burning the Disk on Windows XP, you'll can do it with Nero or Roxio or ISO burner, etc.. Once everything is ready, pop in the Disk in the CD/DVD drive and select the First options from CD-Rom in the Bios Settings or simply boot up and keep tapping the F8 and select "Restore...." or "Repair...." etc.. If restore doesn't fix or is not accessible, you can try the "Repair.. and so on. I hope you know how to do all these, if you have problem, please don't forget to let me know with all your system's details, otherwise it's not possible to give you specific detailed instructions.
There's another options, this is only to recover your files and you'll need to reinstall the windows (I don't recommend installing over the current installed o.s. but a new install after the partition is formated). You can use Windows Live Cd (Xp or Vista or 7, if the current install o.s. is xp, then use XP Live Cd and so on..), there are numbers of torrents seeding on the net, if you need one, i'll help you download after I am confirmed. You have to use the Live Cd to boot your system as you boot up the windows normally, but in reality it, the o.s. is installed on the Cd and at least you'll be able to access the files on your computer so that you can transfer them to other computer. The features and functionality of the Live Cd may have few restrictions, but definitely, to restore or to save your files, this is the best option.
Another Live Cd, not exactly windows, but Ubuntu Live Cd, I hope you heard about Linux, there are many download iso files available online, I'll help you get them (Linux/Ubuntu is a freeware) if you need.
All these are the options you can do for now. Please note that if you have critical and important data on your computer, you must restore no matter what, else you may loose, Recovery softwares are not 100%, so please be careful. This is not a simple task, but now it's a must to do to get your system worked....:-)
Let me know when you are done or if you have problem doing all these, but please with more details.
Thanks for using FixYa.