how do i find ANY obsolete software in my pc, running windows XP

We had a virus problem last month. Our Kaspersky 6.0 wasn’t able to detect the virus because it’s not updated, we didn’t have internet connection until last week. The virus had corrupted important files of some applications and we ended up having trouble installing new softwares, so we then decided to repair the OS using the Windows installation CD. It went well. Programs are now running smoothly and we’re able to install new softwares. But here’s the problem: WMP cannot play audio files. We get this error "Windows Media Player cannot play the file because there is a problem with your sound device. There may not be a sound device installed on your computer, it may be in use by another program, or it may not be functioning properly." Volume control is also missing from the system tray. In the Device Manager, there’s a yellow exclamation mark on "Realtek High Definition Audio". We installed Realtek Driver from the mobo CD — No go. Got an onboard audio. Mobo is ECS 671T-M. Help please…
Thank you for all the response! I appreciate it! But we still got the same problem after installing the driver from the Realtek website. If this might help, here are the things under "Sound,Video and Game Controllers" in our Device Manager:
– Audio Codecs
– Audio Codecs
– Legacy Audio Drivers
– Legacy Video Capture Devices
– Media Control Devices
– Realtek High Definition Audio ** (with a yellow excamation mark)
– Unimodem Half-Duplex Audio Device
– Video Codecs

I’m not sure if one of these is causing the problem… Do you think I should uninstall/remove all of them and reinstall Realtek?

a work computer got infected with advance xp defender, later on the computer was infected with spyguard, password proctect and advance xp fix. by that time the computer was unusable. i did a little search and malware bytes antimalware was the way to go. the virus got removed but now the computer wont start. as soon as windows explorer loads. it stops in the blue screen and halts in error 0x50. i search around and its caused by bad drivers loaded by the virus. i tried to erase those drivers in safe mode but they are locked even tried file assasin but still wont load.
i need to fix this asap a lot of accounting software and clients information in that computer.
the computer only loads in safe mode with command prompt
but if i load explorer it crashes
and reformating its not an option at this moment
can i repair windows with out reformating?
Please help
sorry about the long question but tried to be as specific as i can.

was told program was hidden until accessed