Black screen

hi everybody,
here is the story..
I m using win XP pro SP2.My computer was woring fine but yesterday i have installed a software and then removed.After that when i restarted my comp.,saw it took more time to restart,having some error msgs from avast that avast is having some problem with zone alarm firewall.then i removed zone alarm and restart my comp.now i ran avast,adaware,spybot and restarted again but this time it took 7-8 mins.to shutdown
Again the new problem was it removed all my bookmark stored in mozilla firefox but not stored in opera.now whenever i tried to open mozilla it got hanged.
After getting some suggestion from a friend i repaired my win XP from CD rom with win xp cd.Repair was successful and i worked with my comp. in night.
now when i started my comp. in morning window welcome screen came but after that..... nothing BLACK SCREEN.After waiting 10-15 mins. i shutdown it by holding start button of CPU for few seconds and restarted again but the story was same.
I have very usefull data in my D-Drive and i want to save that.

Any help would be greatly appreciated.Thank you

 

Does it boot into Safe Mode? Press F8 when it is booting to get the boot-up menu.