Ubuntu 11.04 prefix error

Are you using Wubi?
http://ubuntuforums.org/showthread.php?t=1775237

No I am not using Wubi

The thread you linked is a different problem, is it not? Seeing as I have been running 11.04 for a while with no error.

Boot vista, go to Disk Management and take a screenprint. I guess you could use imagebin.org (not sure what the recommended site for this is).

Basically you say you are not using Wubi, but that "NTS5" part seems suspicious.

Also, from the grub prompt, run "set" and write down the results (can't copy and paste unfort).

I apologize I was wrongly informed by my friend it was installed using Wubi.
Here is the output for set.
grub> set
?=0
color_highlight=black/white
color_normal=white/black
lang=
pager=
prefix=(memdisk)/boot/grub
root=memdisk
show_panic_message=true

Will link the Disk Management in a sec.

Here is the Disks

http://imagebin.org/160823

Okay ... so the problem is likely that the root.disk is missing or corrupt. You can check this by looking for C:\ubuntu\disks\root.disk

If it exists, then it might be corrupt and require an fsck: https://wiki.ubuntu.com/WubiGuide#How_can_I_access_my_Wubi_install_and_repair_my_install_if_it_won.27t_boot.3F

If you don't find it, change Windows Explorer settings to show hidden files and folders and go looking for a C:\FOUND.000 folder - sometimes windows will remove corrupted files.

Wubi's root.disk can be corrupted by forcing a shutdown when it's hanging. Instead you should use Alt+SysRq R-E-I-S-U-B.

If you still cannot find the root.disk (use windows search; also note that chkdsk may rename it chk000.chk or something like that so look for a large file matching your wubi install size), try running chksdk /r again (easiest is by right clicking Computer, Properties, Tools, Check disk for errors, fix automatically... reboot to complete) and look again.

Final resort - boot an Ubuntu CD, mount your windows partition and look again. I've heard of some people seeing a corrupted folder in linux that's not visible through windows.

What would the Wubi file size be?

It depends on the size you chose when you installed. (between 3 and 30GB). The actual size will be about less than the install size e.g. if you chose 7GB it will probably be 6.6GB.

I tried searching the first two hidden file names you said and nothing, now doing the chkdsk /r but it is saying cannot lock current drive

you either need to run it off a repair prompt, or reboot to complete. If you follow the instructions I gave in a previous post it shows how to do it through the gui and then it will tell you to reboot). I think the command line option "/r" includes "fix automatically" as well as "check for bad sectors" so you could do both. I normally just to the fix automatically, but that's up to you.