This problem started a couple of weeks ago and seems to be getting progressively worse. Basically I am getting spikes of 100% HDD Usage (with less than 100 KB/s I/O levels) at random intervals while web browsing, word processing, etc. There doesn't appear to be any particular file/program/service that is causing excessive disk usage. It usually lasts between 3-5 minutes during which time PC is horrendously laggy and semi-frozen. Happens about once or twice per hour now. CPU and RAM usage is perfectly normal.
I have scanned the PC with several programs and no malware/viruses were detected. I have not been able to get Chkdsk to run no matter what (command prompt, safe mode, etc). Ran disk defragmenter but did not help. I also tried the PassMark Disk Checkup, but it was not able to complete, said "failure of read element" after 10% complete.
Here's a screenshot I took from my task manager after one of the spikes:
PC is an All-In-One
Windows 7 64-bit
2TB 7200RPM HDD
8GB RAM
i7-3770S CPU
Thanks in advance for any help!
I have scanned the PC with several programs and no malware/viruses were detected. I have not been able to get Chkdsk to run no matter what (command prompt, safe mode, etc). Ran disk defragmenter but did not help. I also tried the PassMark Disk Checkup, but it was not able to complete, said "failure of read element" after 10% complete.
Here's a screenshot I took from my task manager after one of the spikes:

PC is an All-In-One
Windows 7 64-bit
2TB 7200RPM HDD
8GB RAM
i7-3770S CPU
Thanks in advance for any help!