windows vista won't boot up and shuts down

[briare]

Hi, I am a new to the site and need some help. My Toshiba sattlelite e105 laptop developed a problem of shutting down and not able to boot up fully. It is half a year since the 2 year warranty expired. The message said window needed repair so I took it to a repair shop and he charged $200 for reformatting and reinstalling the vista home premium and recovering my data. It worked for about 3 hours then I could not connect to the internet, the bps speed was so slow so I had to take it back for another reinstall.

He said he may have to install a new hard drive if I continue to have same problem. This time the computer connected to the internet and worked for half a day and then same problem again of shutting down by itself and not booting up fully came up. Same message that window needs repair so I have to take it back. Tonight the check dsk actually ran all the way through and then it shut down. It has been really frustrating 21/2 weeks as my yahoo contact list was hijacked before this.

Any suggestions on what my problem might be? I am not sure I want to sink any more money into this as the computer was around $1100.. I wish I knew more about computer repairs. Thank you for your attention and help.