It most probably has a virus or is built up with temporary files and other junk:
Make sure you have uptodate antivirus software and clear temporary files and cookies etc. We also recommend you do a de-frag. for any help with this, or if it does not solve you problem just contact us.We also offer special prices on most Antivirus Suites. and they come free with our new and second hand pc’s
You are using Norton Antivirus, Trend Micro Antivirus or McAfee Anti-virus:
These tend to be quite resource hungry and can therefore slow down older computers. Our suggestion is to install a less resource hungry anti-virus software. please contact us for solutions.
You are still running the same version of windows that came with the computer:
We generally recommend re-installing windows every year to clear up built up files and solve problems.