Computer slow with errors

I am trying to help my father get his computer working properly. A few months ago he had a virus, a trojan codex, he got rid of it with his anti virus program. He has had issues ever since. The computer is running slowly, the internet connection sometimes is very slow or completely halts. I completed all of the step in the read first section and have attached the logs below. Though I selected to create a report on every scan, no report was available from AVG, though it did delete one tracking cookie. While running MGTools i did have the 16-bit error message and followed the steps to fix it. After I completed and rebooted the computer the command prompt window popped up about 5 times and quickly dissappeared and then this error came up.
"Monitor_dlcc_0_running:dlccmon.exe Application Error
The instruction at "0x7c9l0de3" referenced memory at "0x000020c1". THe memeory could not be read. Click ok to terminate the program.
Following that everything seemed fine, but I thought I should mention it.

Since after the virus everytime the computer is restarted it stops on a black screen with the following:

Phoenix ROM BIOS Plus Version 1.10 A00
Copyright 1985 - 1988 Phoenix Technologies Ltd.
Cpyright 1990 - 2005 Dell Inc.
Dell DM051 Series
Bios Version A00

Drive 1 not found. Serial ATA, SATA-Z
F1 to continue, F2 to run the set up utility

By pressing F1 the computer continues to load and go to the log in screen.
His system information is as follows:
Microsoft Windows XP
Media Center Edition
Version 2002
Service Pack 2
Dell Dimension DM051
Intel Pentium 4CPU 3.00 GHz
2.99 GHz, 1.50 GB of RAM

Please let me know what steps I should take next. Thank you in advance.
Eliluca06

 

TimW,
Thank you for your time. I have done the steps you listed. We have not had any printer errors. However I could not locate PartyPoker to remove it. When I ran Analyse.exe the following files were not on the list:
O4 - HKLM\..\RunOnce: [SpybotDeletingA2417] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_28 PM_171.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingC9765] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_28 PM_171.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingA1829] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_32 PM_968.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingC7326] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_32 PM_968.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingA7857] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_19 PM_812.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingC4417] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_19 PM_812.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingA5538] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_33 PM_296.log"
O4 - HKLM\..\RunOnce: [SpybotDeletingC344] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_33 PM_296.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingB7453] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_28 PM_171.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingD6072] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_28 PM_171.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingB9273] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_32 PM_968.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingD4476] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_06_32 PM_968.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingB7785] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_19 PM_812.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingD8429] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_19 PM_812.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingB9841] command /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_33 PM_296.log"
O4 - HKCU\..\RunOnce: [SpybotDeletingD8303] cmd /c del "C:\Documents and Settings\McCutcheon\Application Data\AdwareAlert\Log\2007 Oct 31 - 09_10_33 PM_296.log"

The computer is still asking for us to press F1 on startup, saying that the Drive 1 could not be located. The speed does seem to have improved, however my father thinks his internet is somehow corrupted. I really have no idea as this is not my expertise. Is there anything we can do about the Drive 1 message? Thank you again for your help.
Eliluca06