Vista - Updates will not install

A few days ago, an update appeared for the Last.fm software I am using. When
I clicked to go through this it would not complete the update, where it used
to do this it now says it cannot finish.

Today I noticed that updates also failed for Windows Defender (from both the
Defender and Windows Update) and Norton Secuirty Scan (from Google Pack).

Come to think about, it seems that there have been a few install issues of
this kind recently.

I cleared the temporary update files following a KB thing, which helped
install the Windows Defender update along with an Office 2003 Secuirty
Update, Vista Update and video card driver. However the Norton Security Scan
definitions and update for Last.fm with Windows Media Player still fail.

I am running Windows Vista Home Premium, 2GB RAM, 120GB HD with 37GB free
(until I move pictures and music to my additional 160GB external drive soon).

I Am Having Trouble Signing On To The Internet At All. Every Since I Said Ok To Norton I Can't Sign On, And It Will Not Finnish When I Try To Do Windows Update. I Need Help