|Since you are not specific on what is slow and sketchy about system details, I need to be general. Include more details for more specific help.|
Remove excessive programs from starting with Windows. Use msconfig start tab.
Use Disk Clean up, check nearly everything and run monthly.
Uninstall programs you never use.
Run Disk Defragmenter, if there was a lot of fragmentation, run it again when it is finished. Run defragmenter every 2 or 3 months with XP.
Clean out browser's History, Cookies, Temp Internet Files, etc., repeat weekly. Set Cookies to be deleted when browser is closed. Set to keep history for one to three days instead of longer.
Scan your system with Malwarebytes to verify you are clear of infections.
1GB memory is generally fine for XP but depending on the programs you use, consider increasing to 2GB of memory.
If you are using Norton or McAfee for your antivirus program, know that these are notorious system hogs and are not even as effective as other free options. Try changing to Avast (free version), Microsoft Security Essentials (free) or Webroot's newest offering (free trial only).
If you are using graphics intensive programs or games, consider upgrading or adding a graphics card.
Stay far away from programs and sites that claim to speed up your computer!!!
Unrelated, but important anyway: Don't forget to back up your important personal files to a separate drive.
Post back results and detailed specs and issues for more help.
You have to be a little bit crazy to keep you from going insane.