I just scanned the file myself for viruses using Microsoft Security Essentials and it did not return anything.
Vista7.dll came from a trusted source and it also doesn’t raise any warnings on my AV. If you don’t want to use vista7.dll you can delete the file and use L2Loader.bat (you will get this file after you update your client).
As far as Fire.dll, since it was developed such a long time ago I’m sure it doesn’t comply with today’s standards for coding and therefore raises an error. Here are some related results with people having issues even on the official servers:
Hope this helps.