Windows Vista hangs on Welcome screen

I had a HP desktop PC running Windows Vista that sometimes hanged on the Welcome screen (displayed after entering the password to login). The problem occured randomly but started to occur more and more often causing trouble for the user. Just waiting for the Welcome screen to dissappear (for hours) didn’t help.

I applied different solutions found on the Internet including registry changes, uninstalling HP credential manager and others. One solution suggested on the Internet forums was to reformat the machine and factory install it. Not a preferred solution but ultimately the only thing left to try. 

The machine ended up in my workshop but before formatting it I opened it while running on my workbench. I noticed this machine had a built in flash drive used for Windows Readyboost (in order to make the machine boot faster and load programs faster). I was a bit curious since I hadn’t seen this solution before. The flash memory was connected to the motherboard through a cable. I accidently touched the cable gently and immediately the flash drive dissappeared and reappered in Windows opening the screen asking me what I wanted to do with the newly inserted flash drive. 

This made me suspect that the cause of the problems has been the readyboost located on a flash drive with a poor connection. I disconnected the flash drive completely and the machine have never again had the "hang on welcome screen" problem. Although it doesn’t load programs as fast as before it is way better for the user to have a machine that doesn’t hang on the welcome screen.