PC performance suddenly degraded - multiple issues

Hi,

I have been tearing my hair out over the last week or so, with my PC suddenly showing a noticeable drop in performance.

Operating System: Windows 7 Home Premium 64-bit
Packard Bell: ipower G5800
Processor: Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz (8 CPUs), ~2.9GHz
Memory: 8192MB RAM

By an large it has been a pretty reliable piece of kit and I use it for
a) media streaming around the house (Plex for video and Sonos for audio)
b) online gaming *(Elder Scrolls online, Star Wars The Old Republic etc)
c) surfing
d) general light home use (office etc)

I have two NAS drives (WD "MyBookLiveDuo") which ran fine, but a few weeks ago they suddenly become inaccessible. No idea why, but seemed to resolve it by loading Windows updates. It was actually my wife that found that solution before I did, by doing that on her laptop.
Not long after that I began to sense a general degradation in performance but not too noticeable. It began to get more persistent problems (when playing online i started to get and distortion on sound). This wasn'yt just on line, I began to have local sound issues (through Itunes and Foobar). Then over this weekend, when I tried to use Sonos, i got "network connection speed insufficient to support playback buffering". The sonos devices are all wired rather than wireless. BTW the sonos devise playback 'internet based radio ok' ( a route which would cut the PC itself out).

My gut feeling is that this is a PC issue and not a network issue (but happy to be corrected). When I run a broadband speed test from the PC I get 10MB/s which suggest to me that the internal network must be that fast as well (again happy to be advised otherwise).

I have run sfc scannow and this came back showing no issues with the Windows 7 installation itself. I have downloaded Malwarebytes and run, removing any PUP (so looks clean to me). My virus checker (AVG) is also not reporting any issue.

Whilst looking in Task Manager there does seem to be a correlation in CPU usage when I get the 'genera' sound distortion on the PC (say listening to iTunes) and is easily replicated by simply browsing (I use Firefox as the browser).

I think I need a more systematic approach to solving this one, so welcome any help on diagnosing and resolving any underlying issues.

I suspect that there may be more than one issue, and might need to have more focused thread, but this is my starting position.

Thanks

Alan

Lots of views but no feedback, so a brief update what I have done in the meantime. Using the below article,

Troubleshoot Application Conflicts by Performing a Clean Startup

I followed the steps and the performance did improve when using a clean start up. However, after several hours I wasnt able to pin down to specific causes, but rather it seems that three main players seem to be actve when I replicated the fault.

AVGnsa, Firefox and NT System & Kernel. The first two I have tried running with avg disabled and firefox in safe mode, but still doesn't seem to have cleared the problem.

I have been collecting some screenshots along the way, but not sure that they are of much use. Hope that someone reading this might give me a gentle nudge into what information I should be looking into ...

Thanks

Hi, thanks for you response.

I have uploaded images of msconfig (startups and services). I don't particularly have a slow bootup time, but happy to take any advice on things. Both appear to be bloated on the face of it (services particularly).

Re the AVG, I hear what you are saying, but haven't taken any steps to change anything yet, so still have AVG as I write this update.

Thanks again,

Alan

I continue investigations here, and are looking into ResMon there are signs of excessive Deferred Procedure Calls and Interrupt Service Routines (DCP) which may link to the excessif NT System & Kernel usage too. So I downloaded LatencyMon and wow, did that shed some light immediately (or is it a red herring?). (screen shots 1 and 2). I updated the driver (despite Windows telling me it was up to date)

AS can bee seen there is a lot of 'red' and ndis.sys looks like a good place to start. On my machine I have a Ethernet network card and no wireless devices, so all network activity should be 'wired'. I disabled the network card and checked out the effects in LatencyMon (screen shots 3 & 4). Still some red, but a significant enough change to suggest there is an issue in the ndis.sys (network card) worth investigating.

I am considering picking up a new network card to see if that does anything at all - but not optimistic that it will. Online postings suggest this has worked for some people but not enough for me to think this is the 'single fix'.

Anyone got any ideas about ndis.sys, how to check if its been corrupted? how to refresh?

Thanks