computer does not come up!

Dear sirs,
I was searching all sources I could find to get a solution for my problem and I found this site and people here really helpful so I became member.

I have a Vaio VGN-FE 890 which has a Vista business on it and I never had a problem with it. Two weeks ago I changed my rams from 2 GB to 4 GB and its battery as well and it was working without any problem.

today after connecting it to internet after 2 weeks my anti virus which is Kasper sky 7, updated itself and asked for a restart. I restarted it and it was working without any problem, I updated its rating "Windows experience index" and some other normal daily things like checking some web pages then as usual I closed all open web pages and hibernated it, but I don't know why when I came back home and I turned it on after showing that Vaio screen which comes at the beginning windows didn't start and a black screen without even courser was the only thing I could see.

I shut it down physically by pressing and holding power button several times and I checked BIOS setup but nothing!

I don't really know what to do because I don't know whether this is a physical error or something with windows; and I don't have any boot able CD or anything and I really need my data on hard drive because my thesis that is about to finish is on it and I don't have any backup.

The funniest thing is: This laptop is made in USA and I bought it from Iran and I live in Turkey so I could find no way to register it because neither Sony US nor Sony Europe let me register it and I have no access to Sony's online support!

Can any one help me with this issue please?
Hi coyote_k13, welcome to NST

It was most likely applying system updates it had downloaded in the background, though there have been several problems with Vista hanging after resume from hibernation/sleep.

As you boot the computer, press F8 continually until you get an advanced options boot menu. Try last known good configuration and than if that doesn't get you in, safe mode. Use system restore to put the computer back in configurations a day or so or before the problem began. If it continues, you will need to download our recovery disc from this site. See here for the download and here for the repair proccess.

Dear Friend,
Thank you too much. My problem has been resolved completely and problem was as you guessed.
I used the links you had sent me. I found them really useful and well prepared.
Thank you :smile:
It will not boot in regular mode. It goes trhrough to windows is starting up than stops I tried changing pass worfd in safe mode but it still goes dead
Hello Mhvishal. Welcome to NST.
Have you tried "Last known good configuration" mode? You should also try using the recovery disk downloadable on this site, if that fails. It could be a problem with the BCD or BOOTMGR.