My friend's Vista Home Premium computer was running painfully slow so I opened up Process Explorer and saw that the Svhost (Network Services) instance was spiking to 100% usage, roughly every 20 seconds. I checked out the threads, and the culprit seems to be NLASVC (Network Location Awareness Service). I verified this by suspending this thread in Process Explorer, which stopped the CPU spiking.
A few other things I've already tried that have not helped:
1. Disabling UPNP services
2. Disabling DNS cache service
3. Disabling Anti-virus software (Avast)
4. Replacing the NLASVC.dll file with a fresh version
I did notice that even though disabling NLASVC stopped the 100% cpu spikes, the dnscache thread would still cause a minor spike of 6% cpu at the same interval as the massive NLASVC spikes.
The computer isn't showing any signs of malware and is otherwise working fine.
Thanks for the help,
Edited by orangewedge, 02 April 2014 - 01:37 PM.