Hello, welcome.
1) Uninstall Daemon Tools. Then use this installer/uninstaller to carefully remove (not update) sptd.sys:
Link Removed
Reboot and install PowerISO to replace it. Emulation part of the software is free forever and will never crash Windows:
PowerISO - Create, Edit, Compress, Encrypt, Split, Mount, Extract ISO file, ISO/BIN converter, Virtual Drive
2) Type systeminfo in a command prompt. If your Realtek lan is 8111, use the following link to update. If anything else, search the left side of the link for the update:
Rt64win7 Rt64win7.sys Thu Feb 26 04:04:13 2009
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3) If issues persist, uninstall Avast! in safe mode using the tool found here:
AV Uninstallers - Windows 7 Forums...