The flashing (?) on a folder means that your Mac can't find a bootable system.
That can mean several things:
1. The hard drive has failed. (If the boot drive is original, it may have simply worn out, or the drive bearing have failed, making the drive run too slot, several other possibilities, but all end up meaning that the drive may need to be replaced)
2. The system software is corrupted, maybe some important system file has been accidentally deleted, so the boot system is not complete. So, this might be fixed simply be reinstalling the operating system. If you still have the original system installed, then you may still have the DVD that came with your Mac when new - probably OS X 10.6. Assuming the DVD drive still works, you can reinstall from that original DVD. If you have kept updating, and your 8 year-old Mac has something recent, like Sierra or High Sierra, you may have the installer for that. Usually, you can boot to the recovery system, but a failed hard drive may not work well enough for that. There's a possibility that you can reinstall using the Internet recovery option, but that may not give you a reinstall for the system that you now have installed, but could work with an older system.
But, if the hard drive is failing, this may all be a waste of your time (because it won't do any good to try to install the system on a hard drive that is failing --- you can't fix a failed hard drive, you can only replace it.