STOP 0x000000F4 and other errors, freezing Options

[teiresias]

Specs: Windows XP Professional SP2, 2002 version
Processor: Pentium® 4 CPU 3.40 GHz
1.00 GB of RAM
2 hard drives: C:\ = 144 GB (27.0 GB free), G:\ = storage = 298 GB (33.1 GB free)
Audio: Onboard SigmaTel, previously had SoundBlaster Live! 24-bit before it broke, received new soundcard for Xmas but want to take care of the problems in this post before installing it (though software/drivers/etc. are still installed for the old soundcard)
Any other specifications I should include?
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I realize that the 'Before you post about a problem' pinned thread notes that I should put one problem per post, but all the different errors seem interconnected and can be tied to the 'problem', so I figure I should include them as details.
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Problem: Lately my computer has been very finicky, often freezing completely and necessitating reboot with the power button. There were several errors that preceded it, however.
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History: A few days ago I attempted to transfer a ~2GB folder (2.7 on disk) with ~2700 subfolders containing ~235,000 files from My Documents in C:\ to G:\ as I was worried my C:\ would fail so I'd been moving everything 'important' file-wise to G:\ while keeping programs etc. installed on C:\. The transfer had errors and stopped/froze, so I would hit the power button and attempted again. After it froze and I restarted, Checkdisk informed me that G:\ was dirty and would run its processes, but always got stuck / frozen on a percentage between 10% and 20% on step 2/3. I know it was frozen because I allowed it to sit there and waited overnight more than 12 hours and when I checked it again it was still on the same percentage whereas the previous percentages before it had ran by quickly.

So, I finally got it to run in safe mode by selecting that before Chkdsk would run (it froze if I attempted Safe Mode With Networking, and ran Chkdsk prompting the percentage freeze if run on normal mode) and did some looking around. I found that the corrupted files were in the subfolder of G:\ which I had been transferring from My Documents, and tried to delete it both through Windows Explorer and the command prompt (am novice at the latter), but it didn't allow me. I then manually folder-by-folder deleted every subfolder and file that wasn't corrupted, after which only the corrupted files (less than 100 out of the ~200,000) remained. After that, it restarted and then was able to run completely through all three steps of Chkdsk, and was able to login with Normal Mode. Now that the files were no longer corrupted (I think - Chkdsk had said it was Correcting / Deleting files, then Recovering orphaned file [xxx] into directory file [xxx] with [xxx] changing rapidly, then part 3/3 was Verifying security descriptors and it said it was "Correcting errors in Master File Table's (MFT) BITMAP attribute [xxx] in volume bitmap", but it ran quickly so I couldn't write all the Chkdsk processes down) I deleted the entire tree of the folder in G:\ that had contained the subfolder which had corrupted files in its folders through rmdir /s in the command prompt.

It still froze constantly while working in Safe Mode as well as later/now in Normal Mode - the freezing seems sometimes to be when I attempt multitasking that would never before be too much of a burden, like unzipping a small file that would take seconds as well as scrolling down a Firefox page as well, or attempting to listen to music in Winamp while clicking on a folder in Explorer, etc. The other thing that would prompt freezing was if I would leave it idle / sitting there for a while, even if programs were running (I tried AVG virusscan a couple times but that froze in the middle) so I kept always using the mouse / typing / etc.

I had run Disk Cleanup in C:\ (got rid of over 68 MB of temporary files) while it was starting to freeze but I could still run it in normal mode and hadn't gotten the Chkdsk "G:\ is dirty" thing at startup yet, and attempted to defrag C:\ but it notified me that I needed at least 15% free space (apparently I had 12% free on one and 9% free on the other).

At one point, starting while I was defragging C:\ but continuing after that froze and I restarted, I lost audio and video capability for a while, but that has returned and I no longer worry about it. When reading online I wondered if not enough free space could be to blame, so I greatly reduced the allotted disk space for each drives for Recycle Bin and System Restore, which actually took up more than was available (I think).
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Now, for the error messages: There have been two blue screens, many many many freezes, and many Warnings / Errors in the Event Log. The original blue screen I got was Kernel_stack_inpage_error when I left it on overnight running a program (never had problems with that before), and just today after all the aforementioned steps yesterday I got "STOP: 0x000000F4 (0x00000003, 0x866531C8, 0x8665333C, 0x805D1204) beginning dump of physical memory" which according to Microsoft is this, Kernel_data_inpage_error as opposed to my previous Kernel_stack_inpage_error (forgot to write down the number, sorry!)

Event Log has been having a field day, but there are only 4 relevant that have simply been repeating themselves over again:
1. In 'System' I am very often getting the warning "An error was detected on device \Device\Harddisk1\D during a paging operation" with "disk" as source
2. In 'System' with 'atapi' as source I repeatedly get the warning "The driver has detected that device \Device\Ide\IdePort1 has old or out-of-date firmware. Reduced performance may result."
3. In 'System' with 'Browser' as source I repeatedly get the warning "The browser was unable to retrieve a list of servers from the browser master \\D35XGW1 on the network \Device\NetBT_Tcpip_{406CF207-4E87-4AB8-AF36-A06DDFC5960A}. The data is the error code."
4. A short while after #3 it seems to lead into the Error (in 'System' with 'Browser' as source) "The browser service has failed to retrieve the backup list too many times on transport \Device\NetBT_Tcpip_{406CF207-4E87-4AB8-AF36-A06DDFC5960A}. The backup browser is stopping."

Unfortunately, the events in the Event Log are gibberish to me. Nothing else of consequence has been happening there, however. I would extremely appreciate any help you could give, whether it be suggestions for how to go about correcting the problem or simply explaining what the error messages / event log entries mean - I have no clue what firmware, kernels, Ide, etc. are. Please name anything you want me to try and post results / specs / etc. and I will comply! I am very worried as G:\ was supposed to be my backup drive that I could store everything important on when C:\ finally goes too critical to solve save wiping / formatting it and starting from scratch again. I keep 'patching' C:\ up but know it will fail someday ... didn't expect G:\ to get affected! Help?