正则替换图片地址

[ioriioriii]

<img src='My/UploadFile/2012-10-20/6d3344f515064d568c9574ed339520c7.jpg' alt='' /><br />
<img src='UploadFile/2012-10-20/b7ffbc3a5c4043bb9daf334856728024.jpg' alt='' /><br />
<img src='UploadFile/2012-10-20/fbb2d6bc0376458bb399e3ef1a5712d1.jpg' alt='' /><br />

想要替换所有src地址成

<img src='http://www.aaa.com/UploadFile/2012-10-20/6d3344f515064d568c9574ed339520c7.jpg' alt='' /><br />
<img src='http://www.aaa.com/UploadFile/2012-10-20/b7ffbc3a5c4043bb9daf334856728024.jpg' alt='' /><br />
<img src='http://www.aaa.com/UploadFile/2012-10-20/fbb2d6bc0376458bb399e3ef1a5712d1.jpg' alt='' /><br />

Content = Regex.Replace(Content, "(?i)(?<=src=(['""]))([^'""]+?)(?=\1)", "http://www.aaa.com$2") 这样写的话 最后的结果是
<img src='http://www.aaa.com/My/UploadFile/2012-10-20/6d3344f515064d568c9574ed339520c7.jpg' alt='' />
但是不能替换掉My 应该怎么实现如果有My就替换成空？

[这个还能被注册？]

string temp = Regex.Replace(strs[i], @"(?i)(?<=src=(['""]))([My\/]+)?([^'""]+?)(?=\1)", "http://www.aaa.com/$3");