Some software doesn't show up in 'add/remove programs'. Try going to Start > Programs to look for the name of the software. Sometimes you'll find that the program has its own uninstaller which is shown alongside the main program entry.
Ideally, you should uninstall the software first before attempting to re-install it. If you can't find a way of uninstalling it, just try re-installing it anyway. (Some installation programs will automatically overwrite older, possibly corrupt files. Others won't).
If that doesn't work, try using System Restore to take your PC back to a date when things worked normally.
(On my PC, I get to System Restores as follows:
Start > Programs > Accessories > System Tools > System Restore.
That's using Windows Me. It might be slightly different on other operating systems. If in doubt, just go to Start > Help and type in 'System Restore').
Lastly, unless your camera is either very old or very basic, it will use removable media (i.e. some sort of memory card) to store the images. A far better way to transfer your pictures to your PC is to use a card reader. You simply plug the card reader into a USB port and put the memory card into the slot. Your PC will then recognise the reader as an additional drive and you can 'drag and drop' your files to wherever you want them on your PC. Card readers used to be expensive but they're now under a tenner in lots of places. (Try Tesco Extra or Asda). If you get one you'll be able to transfer images much faster and you can forget all about needing any software for file transfers.
Chris