Windows XP computer is slow to start up and shut down.

Some factors for pc slowness:

1. Laptop or computer hasn't been managed 

2. Pc is contaminated with malware

3. Hard disk is too full. Eliminate needless things, remove rarely used programs. Don't forget to back up

4. Flaky third-party application. Tool bars and add-ons are particular causes in this place. Remove toolbars (Google, Search engines, ISP-branded, etc.) and look properly at what add-ons are in use in your browser(s).

5. Pc has too many needless programs/processes operating in the qualifications. Handle your Startup:

For XP - How to Repair By Using the Msconfig Application in Windows XP -

For Vista/Windows7 - Begin Orb>Search box>type: msconfig and when this indicates in the Outcomes box above, right-click and select "Run as Administrator".Autoruns is also very useful.

6. Customer is operating a bloated/invasive anti-virus system such as ones from Norton and McAfee. Substitute with a better system. I suggest either NOD32 (commercial) or Avast (free). Avira is also excellent but the 100 % free edition has an distressing nag display (Google for guidelines as to how to turn off this). Customer may also be operating more than one real-time antivirus/firewall/security system.

7. Customer has set up new applications that are processer and/or memory-intensive (Photoshop, AutoCAD, Mathmatica or the like) and doesn't have the necessary components energy.

8. Difficult disk is unable and is in PIO Method (IDE pushes only - not appropriate to SATA drives). This is very considerably slowly (like being returning in 1985). See Hans-Georg Michna's details here 
If the PIO registry fix doesn't "stick" (or you have a SATA drive), the hard drive is probably failing and should be tested.
 
Note: If computer has always been slow, in addition to items above user may have purchased a machine with a less powerful processor and not enough RAM (memory). For normal computer use, 512MB-1GB is usually sufficient for XP; Vista should have a minimum of 2GB; Windows 7 is less demanding than Vista but the minimum of 2GB should also be used.