Windows 7: iTunes Will Not Open.

Uninstalling iTunes now. Will clear registry soon...

I'll edit this post with the results

If you want to speed up your Shut Down, there is a Tutorial here

Just before Cleaning via CCleaner, run Disk Cleanup and Disk Defragmenter.

I would download and open CCleaner and use CCEnhancer for more features. Then go to the Clean Tab, Analyze and run the Cleaner. Next go to Tools (NEVER GO TO REGISTRY) and select Startup, select them all and select Disable and then Remove.

Then click on CCleaner's Uninstall Tab and remove anything you don't need or use. Ask here if you are unsure if it is safe to remove or not, or you could Google it.

Next, read this article:
99 ways to Make Your Computer Blazingly Fast

This guide was intended for Windows XP, but I would ignore Step 2, Step 10, Step 11, Step 16, Step 28, Step 37.

Another guide can be found here:
Optimize Windows 7

I would next run an SFC Scan and a Check Disk Scan.

What I do as soon as I get a computer os open MSConfig, select the Boot Tab and select No GUI Boot, this will disable the Boot Animation.

I would also use MSE and Malwarebytes to check for Viruses and Malware.

1: Delete all playlists.

2: Go to Edit, Preferences and remove all the sources you do not need ( iTunes DJ/Genius, etc ). Just below that, deselect Show list tickboxes and Show source icons. Then change the source and list text to small (unless you have difficulty reading). Under When you inset a CD, change the dropdown box to Ask to Import CD. Click Import Settings and deselect Use Error correction when reading Audio CD's. Finally deselect Automatically receive CD track names from Internet and Check for new software updates automatically

3: Go to Playback tab still inside Preferences, deselect everything and set Subtitle Language to Off.

4: Click on the Sharing tab and deselect everything (same goes for Store and Parental).

5: Click Devices, delete any un-needed Backups. and select Prevent iPod's, iPhone's, and iPad's from syncing automatically, deselect [b]Warn when more than ?% of the data on this computer will be changed. Deselect Allow iTunes audio control from remote speakers and Reset sync history.

6: Click Advanced and deselect everything. Reset Warnings, and Cache and Music Location