If a computer is taking along time to load there are many things that can cause that.
If the computer is as old as I think it is, my bet is a bad hard drive or system corruption or bad ram.
If you want to check the system over I suggest downloading the "Ultimate Boot CD" (UBCD) to help troubleshoot. You need to burn it to a CD or write the ISO to a USB flash drive.
There is 2 tests I recommend you run. 1st is called Drive Fitness Test, you will need to change the drives mode in the bios to IDE or Compatibility for this old test to detect the drive.
Once in the program run an advanced test, its self explanatory. If the test completes with a big green screen, the issue is not the drive, if it completes and shows a big red screen, you got a bad drive.
If the drive is bad I'd say it not worth fixing such an old system. Set the drive mode back to what it was before you started.
The 2nd test I suggest you run is called Memtest x86. Once the test starts it will run forever. You only need to run it for 2 passes might take an hour or so. If no errors are displayed the memory is OK too.
If both tests pass I suggest you format the system with a fresh copy of vista if you have the ability to do so.
On a note Vista was killed of by M$ this past year (2017) and is not recommended to connect to the internet at all unless just for updates.
If you need help doing these tests post back.