IE 7 on volume cache can not exceed 1O24 MB you can overcome it by changing the corresponding key in the registry of course after having saved the old key by exporting

Here is one which corresponds to 1,024 MB in XP sp2

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Internet Settings \ 5.0 \ Cache \ Content]
"CachePrefix"="" "CachePrefix" = ""
"CacheLimit" = dword: 00100000

Key modified for a 3164 MB cache

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Internet Settings \ 5.0 \ Cache \ Content]
"CachePrefix"="" "CachePrefix" = ""
"CacheLimit" = dword: 00317270
To change the value Dword switch to decimal and enter a value greater than the former .
This trick is useful for offline browsing for Internet.