I have read all your minin dumps and there are nine different error codes and only two of the 10 are the same. Most point to hardware issues though they cite essential Windows drivers which are too general to help.
There are two minidumps that cite third party drivers as causing issues.
The first 0xC4 and it points to atikmdag.sys which is an ATI Radeon Kernel Mode driver. If you google this along with Vista there are TONS of people on the Vista Forums that have had issues with this.
The other is 0xD1 and these are caused by faulty drivers or buggy software. In this case the dump cites NETw4v32.sys driver as the culprit and this is an Intel Wireless WiFi Link driver.
But getting back to the hardware error codes there are two things that concern me. First and foremost is that CHKDSK stalls for an hour before passing. This shouldn't be. Couple that with the fact that you have an 0x24 error and it looks like you may have a harddrive failing or at least has some bad sectors.
0x00000024: NTFS_FILE_SYSTEM
A problem occurred within NTFS.SYS, the driver file that allows the system to read and write to NTFS file system drives. There may be a physical problem with the disk, or an Interrupt Request Packet (IRP) may be corrupted. Other common causes include heavy hard drive fragmentation, heavy file I/O, problems with some types of drive-mirroring software, or some antivirus software.
Do this first. Find out the make of your harddrive and go to their website for their free utility to run harddrive diagnostics. If you can't find that information use Seagate's SeaTool utility. It works with many brands and if you do use it make sure you run the Long DST.
Get back to us with the results.
The other error of note is 0x4F and this is a strong indicator of corrupted memory. In fact it specifically noted corrupted memory. I know you ran Memtest but for how many passes? The rule is a minimum of 7 passes and as good as this test is bad RAM has been known to pass it. You might want to try running with one stick in to see if that brings stability and then switch. Or run Memtest per stick.
* I suggest backing up all your important information.