I recently cleaned my computer and took the cpu fan and heatsink off to clean. I reapplied thermal paste and now computer shuts down. If I tighten all screws on heatsink and fan it will do nothing. If i loosen 2 of tnem I can get it to turn on but shuts down within 15 seconds. I turn back on and that is when I get the beeps hi and low and then shuts off. It only beeps about 3 seconds. So is this a bad heatsink, CPU or Mobo Please help. Here are the specs from my computer it is a emachine T5026
CPU: Intel® Pentium® 4 Processor 519
Operates at 3.06GHz
1MB L2 cache and 533MHz FSB
Operating System: Genuine Microsoft® Windows® XP Home
Chipset: Intel® 915GV chipset
Memory: 512MB Dual Channel DDR
Expandable to 4GB
Hard Drive: 160GB Serial ATA 7200rpm, 8MB cache
CPU: Intel® Pentium® 4 Processor 519
Operates at 3.06GHz
1MB L2 cache and 533MHz FSB
Operating System: Genuine Microsoft® Windows® XP Home
Chipset: Intel® 915GV chipset
Memory: 512MB Dual Channel DDR
Expandable to 4GB
Hard Drive: 160GB Serial ATA 7200rpm, 8MB cache