I cannot tell you why you are getting the error. It sounds like the flash thumb drive may need to be formatted, but I don't want to engage into a different issue getting us off track of our original issue.
You can try to format the flash drive to see if that resolves the issue.
To format it, insert the drive. Navigate to My Computer. Locate the drive then right click on it. Choose format. A new small window will open. Place a check mark in the box for "Quick Format". Allow it to complete.
If that doesn't work you can email the file to yourself. Now boot from the Ubuntu disc. Open the internet browser and download the file from your email.
Download the file from HERE.
Mission Accomplished with the Flash Drive. Fortunately I had another
new flash drive to try. It works. The Boot.ini is on the Flash Drive. Will
now go forward with the next steps and get back to you.
Stuck Again. Flash Drive issue resolved, now dealing with other roadblocks
with the ailing computer.
I went into setup to check which primary drive is booting.
Link: Advanced BIOS Features
This is what I see on the screen for Advanced BIOS Features:
Virus Warning (Disabled)
CPU L1 L2 Cache (enabled)
Quick Power On Self Test (enabled)
First Boot Device (CD Rom)
Second Boot Device (Floppy)
Third Boot Device (HDD-O)
Boot Other Device (Disabled)
Swap Floppy Drive (Disabled)
Boot Up Floppy Seek (Disabled)
Boot Up Numlock Status (on)
Gate A20 Option (fast)
ATA 66/100 Cable MSG (Disabled)
Typematic Rate Setting (Disabled)
xTypematic Rate (chars/sec) 6
xTypematic Delay (msec) 250
Security Option (setup)
APIC Mode (enabled)
OS Select For DRAM> 64 MB (Non-OS2)
HDD S.M.A.R.T Capability (disabled)
Attempted to do a Boot from the Ubunta CD (negative)
Computer is Booting from C:\Windows
Computer attempts to Boot, stops, goes to Blue Screen to
Check The File System on C:
Press any key to stop the Check The File System
Goes to Black Screen
Invalid Boot.ini File
Booting From C:\ Windows
Again, Computer attempts to Boot, stops, goes to Blue Screen to
Check The File System on C:
Will wait for followup instructions to break down this roadblock.