File c:\windows\windows32\drivers\sysaudio.sys was infected by backdoor.trojan virus and now is on quarantine by Symantec Antivirus Corporate Edition and I have WinXP firewall enabled. Should I remove this system file or leave it as it is, if it is critical to Windows XP? Also, what may have been the infection reason? Thank you...

All I can say is that I have a sysaudio.sys file in that folder. Its description is System Audio WDM Filter Here http://www.file.net/process/sysaudi... I find that the file is valid. But Malware can have names of valid files.

128MB RAM? XP must be horribly slow! "what may have been the infection reason?" Probably because you're running a crappy Anti-virus program. You won't find many people in these forums singing the praises of Norton/Symantec. Try running a Trojan Remover to make sure your system is clean. This one is fully functional for 30 days...simply uninstall it after the 30 days are up: http://www.simplysup.com/tremover/d... And consider replacing your anti-v program: http://www.filehippo.com/download_a... http://www.filehippo.com/download_a...