Program installation are very slow on vista

[NSA_CIA]

After installing windows vista on my computer i have noticed that whenever i try to install a program it takes too much time to install and after 20-25 minute my system freezes. I can't seem to figure out why this is happening. Anyone have any ideas as to what it could be?

[Lillebror]

This issue occurs if one of the following conditions is true :
You have spyware or malware running on the computer.
You have viruses that are running on the computer.
You do not have sufficient free space on the hard disk.
You do not have sufficient random access memory (RAM) installed on the computer.
You have corrupted or outdated drivers.
You have too many files in the Recycle Bin or temporary folders.

[Wynn]

There are many program which run in background and takes too much amount of memory. Some program also makes pc slow at the time of boot up you can disable this type of program. Click on run type msconfig. The dialog box will appear click on start up tab select the program which you want to disable. Click on save and then exit.

Check this thread to speed up your computer : Top 20 tips to speed up your pc

[SalVatore]

Revo Uninstaller helps you to uninstall software and remove unwanted programs installed on your computer even if you have problems uninstalling and cannot uninstall them from "Windows Add or Remove Programs" control panel applet.

Revo Uninstaller is a much faster and more powerful alternative to "Windows Add or Remove Programs" applet!With its advanced and fast algorithm, Revo Uninstaller analyzes an application's data before uninstall and scans after you uninstall an application. After the program's regular uninstaller runs, you can remove additional unnecessary files, folders and registry keys that are usually left over on your computer.

You can also check this guide to speed up your windows performance :
How To Make Your Windows Fast As Never Before