Just thought I would mention this to anyone having trouble with IE7 and the 'runas' feature
I've been looking into this for quite some time, and have finally managed to resolve the issue.
Please try out and let me know how you get on
1) Right click IE in the quick launch section near the start button, and select 'Run as...'
2) Enter your elevated domain credentials
3) In the address bar, type C:\
4) You will find that your local C:\ will appear in a new window
5) You will now find that this window has your elevated security rights, so you can access control panel, network shares etc.