Removing Backslash with Sed

[R. G. Newbury]

I have large number of scanned images of documents, which have been 
'managed' by a windows program which produces an index page with a link 
to each document, and a document page with links to each page in the 
document. There are about 1400 document pages.
Unfortunately the windows program produces a link in the form:
<a href='..\index.html'><img src='..\header_index.jpg'>
That is: containing backslashes.

I have tried to figure our a search/replace line for sed but nothing I 
have tried works...in part I assume because the '\' is itself the 
'escape' character. Even so, search expressions like '..\\' do not work.

ANyone know how to do this? There are about 20 backslashes in each 
document index page, so I am not even considering a manual method... 
although that works...
Geoff