First, I assume you have Windows XP and that its main folder is C:\Windows.

I don't have those messages either with 1.4 or 1.5. Although I don't normally use the Spybot HOSTS file (I use the one from mvps.org), I just tried adding Spybot's and removing it, and that all worked smoothly.

The path in the first two error message is obviously wrong. As shown, it looks as if it was looking for the Windows folder (%systemroot%) and its subfolders as a subfolder of

C:\Program Files\Spybot - Search & Destroy

and obviously could not find it there.

I don't know why it is doing that on your system, but I don't think it means there is anything necessaily wrong with your HOSTS file per se (it is just a text file, any errors in it would just be ignored), rather that somewhere or other the path to it has got badly mangled. It should just be

C:\WINDOWS\system32\drivers\etc\HOSTS
or
%SystemRoot%\system32\drivers\etc\HOSTS

I don't know for sure, but possibly the other messages you are getting with version 1.5 are as a rseult of the initial error, and would not appear if that were corrected.

When in Spybot, advanced mode, Tools, Hosts file page, does it show the current contents of you HOSTS file (before you click on Add Spybot's hosts list)?

You could check with Windows Explorer, see if the HOSTS file is in the correct place, and only there (you may need to first go to control panel, folder options, view tab, check show hidden files and folders, uncheck hide extensions for known file types, uncheck hide protected operating system files (click yes to any warning message), click Apply OK).
If you want to search for it, click start, search, for files or folders. In the search window, left panel, click on mor advanced options, check the first three boxes. then search your hard drive for hosts. The hosts file has no extension. If you find it, it should open in Notepad. Apart from comment lines which start with a #, the first line should be

127.0.0.1 localhost

thereafter there may be a list of entries (with or without comment lines starting with #) of the form

127.0.0.1 ad.a8.net

the first part should always be 127.0.0.1, the second part is the domain name of the site that is to be redirected.

If you find more than one file called HOSTS without a file extension (the bit after the . in most file names), delete all that are not in

C:\WINDOWS\system32\drivers\etc\HOSTS