OK...but the problem is that there are any number of things that routinely can cause the DMA mode to switch to PIO mode.
I didn't try to list every link of possible causes...because I think it unimportant what the exact cause is on a system...the proposed cure (the registry edits) apply to the symptoms, regardless of cause.
Such a change has happened to many of us, it's not just any one thing which can be corrected.
But...it can be overcome when it happens.
FWIW:
Ataport.sys seems to be a Vista file,
http://support.microsoft.com/kb/943899.
0x0000007A: KERNEL_DATA_INPAGE_ERROR
A page of kernel data was not found in the
pagefile and could not be read into memory. This might be due to
incompatible disk or controller drivers, firmware, or hardware.
Note that it does not say anything about defective RAM.
The pagefile is hard drive space that can be used to help systems with insufficient amounts of RAM...it's more likely (IMO) for a pagefile problem to indicate a
hard drive or Windows problem...than a RAM problem.
You don't have to pay someone to check the hard drive or RAM...you can do those things yourself and be sure that they were done correctly and still have your money in your pocket.
Manufacturer and model of this laptop, please?
Do you have a Microsoft Genuine XP CD? Do you have a Microsoft Genuine Vista CD?
Was the XP install deleted...before installing Vista?
Why change from XP to Vista?
Without the numeric/alphabetic code that accompanied the memory management error...I can't guess what that might point to. But here's one such error, from
http://www.aumha.org/a/stop.htm:
0x0000001A: MEMORY_MANAGEMENT
This memory management error is usually hardware related. See the General Troubleshooting of STOP Messages checklist above. If this occurs while installing Windows, also check the Windows system requirements including the amount of RAM and disk space required to load the operating system. If none of the above resolves the problem, see the MSDN article linked above for further steps.
Now...when I add these things...to the fact that may have had overheating problems...my guess would have to be that you now (after system overheating) have a bad CPU or a bad motherboard...or both.
What I would do to confirm or refute that...a
clean install of the right operating system, with the right drivers. That will give you a good base upon which to determine what is wrong with your system as it exists today.
Louis