Vista won't boot - oxc0000221

Hey everyone,

I just purchased a used Gateway computer with Windows Vista x64.

Upon turning the computer on for the first time (nothing connected other than monitor, keyboard & mouse) I received the following error:

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Windows failed to start. A recent hardware or software change might be the cause. To fix the problem:
1. Insert your Windows installation disc and restart your
computer.
2. Choose your language settings, and then click "Next."
3. Click "Repair your computer."

If you do not have this disc, contact your system administrator or computer manufacturer for assistance.

File: \windows\system32\ntoskrnl.exe

Status: 0xc0000221

Info: Windows failed to load because the kernel is missing, or corrupt.
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So, I popped in the recovery disk and rebooted. After hitting a key to boot from the disk and waiting for the Windows Loading Files bit to take place, I end up at the same screen again-- except now I'll get an \drivers\sisraid4.sys rather than the ntoskrnl.exe file error.

Now, if I go ahead and hit enter on this screen, I'm taken to a new screen:

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Choose an operating system to start, or press TAB to select a tool:
(Use the arrow keys to highlight your choice, then press ENTER.)
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Windows Setip [EMS Enabled]

Below this it states:

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To specify an advanced option for this choice, press F8.
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And below this section it states:

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"Tools:"

Windows Memory Diagnostic

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Hitting enter and trying to boot the Windows Setup just starts the whole thing over again. Entering the Windows Memory Diagnostic tool screen brings up the blue Memory Diagnostic screen, but the computer never actually makes any progress in scanning the computer's memory (just sits there, frozen).

So. Did I buy a broken computer? Can anyone help me here? It's enormously frustrating to purchase a used computer that's guaranteed to be fully functioning, and end up with this. Thanks in advance for your help.