Ok, first off, copy the one on the C: drive and rename the copy "boot.BAC" (without the quotes)
Then copy the one on the D: drive and rename the copy "boot.BAD" (without the quotes)
Right click on the boot.ini on the C: drive, select Properties, then remove the checkmarks at the bottom of the page (For Read Only and Hidden). then click on OK. DO the same thing for the one on the D: drive
Next, right click on the boot.ini on the C: drive and select Open.
Type in so it looks like this (I've bolded the changes that I suggest that you make):
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional_D" /noexecute=optin /fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional_C" /noexecute=optin /fastdetect
Then Save the file.
Next, right click on the boot.ini fiel on the D: drive and select Open.
Type in so it looks like this (I've bolded the changes that I suggest that you make):
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional_d" /noexecute=optin /fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional_c" /noexecute=optin /fastdetect
Then Save the file.
Please note that the _C is associated with partition(1) and the _D is associated with partition(2)
Also note that I used Capital letters for the boot.ini on the C: drive and lowercase letters for the boot.ini on the D: drive (that'll tell you which bootloader you're using.
Then, reboot and tell us which one you see (the one with the Capital letters or the one with the lowercase letters)
Then, if I'm correct in my guesses - it's the one with the "C" that will go to the old infected OS - and the one with the "D" that will go to the one in which the sound doesn't work.
Let us know what you find out.