As there are so many possibilities here as to what it could be, it's probably best to take it in to get looked at. You might want to check out which store if any is running one of their free computer diagnostic checks (i.e. Best Buy, Office Depot, Staples, etc) so you can save $35-60 on the fee. You might even be able to find a coupon off the internet. Gotta save where you can - and hopefully it's nothing too serious. You'd rather spend that money on more fabric - not a new computer! ;)
Explosive blessings, abundance and inspiration to you all!
- The Creative Seamstress