On a vanilla XP, the value of the BootExecute registry key is:
autocheck autochk * The file chkvdisk in your registry entry is, according to the article Chkvdisk not found, part of the RollBack Rx product, which is an instant PC recovery software.
If you have RollBack Rx installed, it might explain why the hard disk is in constant use.
Let me know if this is the case.
EDIT
The RollBack Rx knowledge-base contains this article:
Rollback is causing a repetitive CHKDSK
After announcing that a CHKDSK problem is impossible, the article does actually explain how it can happen. I personally find the following paragraphs to be really frightening:
Rollback Rx ... rather than copy the data somewhere else, declares the hard drive Sectors where the data is currently located as “protected”. It subsequently redirects any attempts to change that sector. It does this by attaching a “filter” to the Windows driver.
So, for example, if WFM (Windows File Manager?) wants to write to sector 100, Rollback detects the write, determines that a snapshot protects sector 100, and redirects the write to an open sector (say, 200) and creates a reference in its own Disk Map. Any subsequent read to Sector 100 is also redirected to Sector 200.
Alternately, a hard power loss just at the very microsecond that Rollback is flushing its Disk Map from memory to disk can cause a Disk Map Error as well as, very likely, a CHKDSK. In this case, the CHKDSK run will conclude successfully, but this does not fix the Rollback Disk Map anomaly, because the Map is invisible to Windows.
Conclusion: RollBack Rx becomes your disk manager, rather than Windows.
In fact, Windows has no idea what's happening to its own hard disk.
The above article contains a section titled "Find and Fix Snapshot Problems", that's supposed to fix these same problems that the same article previously denounced as urban myths. Not having RollBack Rx installed on my computer, I have no way of verifying whether they really work, but you certainly won't find anything better.
All I can remark as regarding installing RollBack Rx on my own computer is :
Over my dead body!