A few things to try...
First off, depends on how old your computer is. If it is older than 3 or 4 years, It is probably never going to get any faster. Microsoft sends UPDATES constantly without TESTING on old computers, they only make sure that it works on new(er) ones. Every update that you apply from them just makes it slower. If it is that old, you can physically clean it. With the power off, open it up and carefully vacuum the inside. if the fans are clogged with lint or dust, it will make it overheat and take F O R E V E R... to start. Take the memory chips out and put them back in. Sometimes if a chip is barely making contact, will cause the computer to totally fail or do what you are describing.
Let us know if you trying these changes anything.
